261531 has 6 divisors (see below), whose sum is σ = 377780. Its totient is φ = 174348.

The previous prime is 261529. The next prime is 261557. The reversal of 261531 is 135162.

It is not a de Polignac number, because 261531 - 2¹ = 261529 is a prime.

It is a super-2 number, since 2×261531² = 136796927922, which contains 22 as substring.

It is a Duffinian number.

It is a nialpdrome in base 8.

It is a zygodrome in base 8.

It is not an unprimeable number, because it can be changed into a prime (261581) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 14521 + ... + 14538.

2²⁶¹⁵³¹ is an apocalyptic number.

261531 is a deficient number, since it is larger than the sum of its proper divisors (116249).

261531 is a wasteful number, since it uses less digits than its factorization.

261531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29065 (or 29062 counting only the distinct ones).

The product of its digits is 180, while the sum is 18.

The square root of 261531 is about 511.4010168156. The cubic root of 261531 is about 63.9500749970.

Adding to 261531 its reverse (135162), we get a palindrome (396693).

The spelling of 261531 in words is "two hundred sixty-one thousand, five hundred thirty-one".