251263561 has 2 divisors, whose sum is σ = 251263562. Its totient is φ = 251263560.

The previous prime is 251263549. The next prime is 251263603. The reversal of 251263561 is 165362152.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 202891536 + 48372025 = 14244^2 + 6955^2 .

It is a cyclic number.

It is not a de Polignac number, because 251263561 - 2⁷ = 251263433 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (251263541) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125631780 + 125631781.

It is an arithmetic number, because the mean of its divisors is an integer number (125631781).

Almost surely, 2^251263561 is an apocalyptic number.

It is an amenable number.

251263561 is a deficient number, since it is larger than the sum of its proper divisors (1).

251263561 is an equidigital number, since it uses as much as digits as its factorization.

251263561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10800, while the sum is 31.

The square root of 251263561 is about 15851.2952467614. The cubic root of 251263561 is about 631.0200666211.

The spelling of 251263561 in words is "two hundred fifty-one million, two hundred sixty-three thousand, five hundred sixty-one".