251531 has 4 divisors (see below), whose sum is σ = 287472. Its totient is φ = 215592.

The previous prime is 251527. The next prime is 251533. The reversal of 251531 is 135152.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 251531 - 2² = 251527 is a prime.

It is a super-2 number, since 2×251531² = 126535687922, which contains 22 as substring.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 251531.

It is not an unprimeable number, because it can be changed into a prime (251533) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17960 + ... + 17973.

It is an arithmetic number, because the mean of its divisors is an integer number (71868).

2²⁵¹⁵³¹ is an apocalyptic number.

251531 is a deficient number, since it is larger than the sum of its proper divisors (35941).

251531 is an equidigital number, since it uses as much as digits as its factorization.

251531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35940.

The product of its digits is 150, while the sum is 17.

The square root of 251531 is about 501.5286631889. The cubic root of 251531 is about 63.1243868189.

Adding to 251531 its reverse (135152), we get a palindrome (386683).

The spelling of 251531 in words is "two hundred fifty-one thousand, five hundred thirty-one".