251533561 has 8 divisors (see below), whose sum is σ = 256624200. Its totient is φ = 246474240.

The previous prime is 251533553. The next prime is 251533591. The reversal of 251533561 is 165335152.

It can be written as a sum of positive squares in 4 ways, for example, as 40005625 + 211527936 = 6325^2 + 14544^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 251533561 - 2³ = 251533553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (251533591) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8745 + ... + 24073.

It is an arithmetic number, because the mean of its divisors is an integer number (32078025).

Almost surely, 2^251533561 is an apocalyptic number.

It is an amenable number.

251533561 is a deficient number, since it is larger than the sum of its proper divisors (5090639).

251533561 is a wasteful number, since it uses less digits than its factorization.

251533561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15659.

The product of its digits is 13500, while the sum is 31.

The square root of 251533561 is about 15859.8096142419. The cubic root of 251533561 is about 631.2460105489.

It can be divided in two parts, 2515335 and 61, that added together give a square (2515396 = 1586²).

The spelling of 251533561 in words is "two hundred fifty-one million, five hundred thirty-three thousand, five hundred sixty-one".