251566 has 24 divisors (see below), whose sum is σ = 467856. Its totient is φ = 100800.

The previous prime is 251561. The next prime is 251567. The reversal of 251566 is 665152.

It is a self number, because there is not a number n which added to its sum of digits gives 251566.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251561) by changing a digit.

251566 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1591 + ... + 1741.

It is an arithmetic number, because the mean of its divisors is an integer number (19494).

2²⁵¹⁵⁶⁶ is an apocalyptic number.

251566 is a deficient number, since it is larger than the sum of its proper divisors (216290).

251566 is a wasteful number, since it uses less digits than its factorization.

251566 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 184 (or 177 counting only the distinct ones).

The product of its digits is 1800, while the sum is 25.

The square root of 251566 is about 501.5635552948. The cubic root of 251566 is about 63.1273145575.

The spelling of 251566 in words is "two hundred fifty-one thousand, five hundred sixty-six".