Whose number starts with 0421?
The 0421 mobile prefix appears in the ACMA register as held by OPTUS MOBILE PTY LIMITED, which holds every one of the window's 1m allocated numbers. The earliest allocation in 0421 is dated 26 October 2000 (to SINGTEL OPTUS PTY LIMITED, since transferred to OPTUS MOBILE PTY LIMITED).
Source: ACMA register, data as of 24/10/2026
The story of 0421
0421 was allocated to Singtel Optus on 26 October 2000, in the same batch as 0422, and transferred to Optus Mobile Pty Limited on 30 January 2003. The register lists the window as a single million-number arc with no other holder — a straightforward second-generation Optus range.
The 0421 ranges in the ACMA register
The 0421 window is covered by 1 allocation with a combined capacity of about 1m numbers, in the hands of 1 holder. The range has changed hands since allocation: the register still names SINGTEL OPTUS PTY LIMITED as original allocatee, with the transfer recorded on 30 January 2003.
| Range | Numbers | Original allocatee | Current holder | Allocated | Transferred |
|---|---|---|---|---|---|
| 0421000000–0422999999 | 1m in 0421 (range: 2m) | SINGTEL OPTUS PTY LIMITED | OPTUS MOBILE PTY LIMITED | 26/10/2000 | 30/01/2003 |
- 0421000000–0422999999 (2m numbers, of which 1m fall inside 0421) was allocated on 26 October 2000 to SINGTEL OPTUS PTY LIMITED and transferred on 30 January 2003 to OPTUS MOBILE PTY LIMITED; the register range runs from 0421 into 0422.
Optus Mobile in 0421 and nationally
OPTUS MOBILE PTY LIMITED holds 1m numbers in 0421 — the whole window — which is a small slice of its 29.4m mobile numbers nationally, or about 34% of every allocated Australian mobile number. The register places Optus Mobile in 24 different 04xx prefixes, including 2 of the other nine in the 0420–0429 decade (0422, 0423).
| Holder | Numbers in 0421 | Share of 0421 | Share of all 04 numbers | Prefixes held |
|---|---|---|---|---|
| OPTUS MOBILE PTY LIMITED | 1m | 100% | 34% | 24 |
The other prefixes in the 0420–0429 decade
Held by Vodafone Australia, Optus Mobile and Telstra: 0420, 0422, 0423, 0424, 0425, 0426, 0427, 0428, 0429. The decade's oldest allocation is in 0429 (18 September 1998, Telstra), its youngest in 0426 (28 May 2010, Vodafone Australia). One prefix in the decade is split between several holders: 0420.
What does a call from a 0421 number mean?
Standard mobile rates. A 0421 number has been possible since late 2000; the prefix tells you the range holder of record, not the network the SIM is on today.
What people check and report about 0421 numbers
From searches typed into this site's lookup form since 3 September 2026, and the verdicts and moderated reports visitors left. A check usually follows a missed call.
Verdicts and reports on 0421 numbers: 1 verdict, 1 report
1 scam. Too few to show shares yet.
Report types: Scam attempt (1).
Most-reported and most-checked 0421 numbers
| Number | Verdicts | Reports | People checking |
|---|---|---|---|
| 0421 363 466 | 1 scam | 1 | 1 |
Had a call from a 0421 number?
No clear pattern in reports on these numbers yet. If a call worried you:
- Call back on a number you trust
If a caller says they're your bank, the ATO, Services Australia, a courier or your telco, hang up and ring the organisation on the number from its website or your statement, never the number that called you. Caller ID can be faked.
- Report the call to Scamwatch
The National Anti-Scam Centre uses Scamwatch reports to warn others and to get scam numbers blocked. Note the number, the time and what the caller claimed to be. If anyone is in danger, call 000.
- Register on the Do Not Call Register
Registering landlines and mobiles is free and stops most telemarketing calls within 30 days. Charities, political parties, surveys and scammers aren't covered.
- Forward spam texts to 0429 999 888
The ACMA collects unsolicited commercial texts forwarded to 0429 999 888 (standard message charges apply). Don't edit the message first. Scam texts that impersonate a bank, toll road or delivery company go to Scamwatch instead.
Nationally, Scamwatch recorded $72.5 million lost to scams that started with a phone call in 2025 (down from $107.2 million), with a median loss of $3,800 per report that lost money, and phone-call scam reports are 73.7% below their 2021 level. Telcos blocked 109.3 million scam calls and 45.2 million scam texts in January to March 2026. Sources: Targeting scams 2025 (National Anti-Scam Centre); ACMA quarterly report, Jan–Mar 2026.
0421 numbers: questions and answers
Which network does a 0421 number belong to?
The ACMA register lists Optus Mobile as the holder of every allocated number in 0421 (1m numbers). Mobile numbers can be moved to another network, so the caller may now be with a different provider.
When was 0421 first allocated?
The earliest 0421 range in the register is dated 26 October 2000, to Singtel Optus. The window is covered by 1 register range.
How big is Optus Mobile's share of Australian mobile numbers?
Across the whole 04 range, Optus Mobile holds about 34% of allocated mobile numbers, spread over 24 of the 04xx prefixes.
Are calls from 0421 numbers scams?
Visitors have left 1 verdict on 0421 numbers (1 scam, 0 nuisance, 0 safe) and 1 moderated report, across 42 numbers people looked up. Most 0421 numbers belong to ordinary subscribers.
How do I report a scam call or text from a 0421 number?
Report scam calls and texts to Scamwatch. Forward unsolicited commercial texts to the ACMA on 0429 999 888, and block the number from your phone's recent calls or messages. If you lost money, call your bank first, then report it through ReportCyber.
This prefix carries 4 distinct register facts — below the 5 this site requires before a prefix page is offered to search engines. It stays available for direct lookups.
Check a 0421 number
Range data is not personal data and the number on your screen can be spoofed. Scam calls: Scamwatch. Guides: Who called me from this number?, Which carrier owns which mobile prefix?