261509951 has 2 divisors, whose sum is σ = 261509952. Its totient is φ = 261509950.

The previous prime is 261509923. The next prime is 261509953. The reversal of 261509951 is 159905162.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 261509951 - 2¹⁴ = 261493567 is a prime.

Together with 261509953, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261509953) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130754975 + 130754976.

It is an arithmetic number, because the mean of its divisors is an integer number (130754976).

Almost surely, 2^261509951 is an apocalyptic number.

261509951 is a deficient number, since it is larger than the sum of its proper divisors (1).

261509951 is an equidigital number, since it uses as much as digits as its factorization.

261509951 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24300, while the sum is 38.

The square root of 261509951 is about 16171.2693070148. The cubic root of 261509951 is about 639.4835930334.

The spelling of 261509951 in words is "two hundred sixty-one million, five hundred nine thousand, nine hundred fifty-one".