251609261 has 2 divisors, whose sum is σ = 251609262. Its totient is φ = 251609260.

The previous prime is 251609243. The next prime is 251609269. The reversal of 251609261 is 162906152.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 139122025 + 112487236 = 11795^2 + 10606^2 .

It is a cyclic number.

It is not a de Polignac number, because 251609261 - 2²⁶ = 184500397 is a prime.

It is a super-2 number, since 2×251609261² = 126614440441932242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251609269) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125804630 + 125804631.

It is an arithmetic number, because the mean of its divisors is an integer number (125804631).

Almost surely, 2^251609261 is an apocalyptic number.

It is an amenable number.

251609261 is a deficient number, since it is larger than the sum of its proper divisors (1).

251609261 is an equidigital number, since it uses as much as digits as its factorization.

251609261 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 251609261 is about 15862.1959702936. The cubic root of 251609261 is about 631.3093295084.

The spelling of 251609261 in words is "two hundred fifty-one million, six hundred nine thousand, two hundred sixty-one".