121
121.5 megahertz is the international aeronautical emergency frequency.
Where 121 fits
Why 121 is special
Satellite monitoring of it ended in 2009, so a beacon transmitting only on this frequency now depends on an aircraft happening to hear it.
121 is part of
Factors & digit properties
- Divisors (3)
- 1, 11, 121
- Prime factorisation
- 11^2
- Digit sum
- 4
- Digital root
- 4
Representations
- Decimal
- 121
- Binary
- 1111001
- Octal
- 171
- Hexadecimal
- 79
- Roman numeral
- CXXI
- Scientific notation
- 1.210 × 10^2
Other mathematical patterns
- Palindromic number
- Deficient number
- Powerful number
- Semiprime
Related numbers & connections
Satellites stopped listening to the analogue distress frequency in 2009 in favour of the digital one.
View 406 →Other connections
- contrasts with406
why?
Strength 0.50, confidence "high".
Technology & computing
121.5 MHz is the international aeronautical emergency frequency. Cospas-Sarsat satellite processing of 121.5 MHz beacons ceased in February 2009 in favour of 406 MHz.
DocumentedTechnology & computingGeography: International — ICAOPeriod: 1950s–
Common questions
Is 121 a prime number?
No, 121 is not prime.
What are the factors of 121?
The factors of 121 are 1, 11, 121.
What is 121 in Roman numerals?
121 in Roman numerals is CXXI.
About this page's data
Mathematical facts:computed directly from the number's value — nothing to source or verify externally.
Contextual records: 1 reviewer-confirmed record, sourced and reviewed before publication.
Last reviewed: 3 August 2026