241 (number) explained

Number:	241
Prime:	twin prime

241 (two hundred [and] forty-one) is the natural number between 240 and 242. It is also a prime number.

In mathematics

• 241 is the larger of the twin primes (239, 241). Twin primes are pairs of primes separated by 2.
• 241 is a regular prime^[1] and a lucky prime.^[2] Since 241 = 15 × 2⁴ + 1, it is a Proth prime.
• 241 is a repdigit in base 15 (111).
• 241 is the only known Lucas–Wieferich prime to (U, V) = (3, −1).

In other fields

• Americium-241 is an isotope commonly used in smoke detectors.^[3]

Notes and References

1. Web site: Sloane's A007703 : Regular primes. The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. 2016-05-28.
2. Web site: Sloane's A031157 : Numbers that are both lucky and prime. The On-Line Encyclopedia of Integer Sequences. OEIS Foundation. 2016-05-28.
3. Web site: US EPA . OAR . 2018-11-27 . Americium in Ionization Smoke Detectors . 2024-08-17 . www.epa.gov . en-US.