21132531 has 24 divisors (see below), whose sum is σ = 35549280. Its totient is φ = 11846016.

The previous prime is 21132509. The next prime is 21132557. The reversal of 21132531 is 13523112.

21132531 is a `hidden beast` number, since 2 + 1 + 132 + 531 = 666.

It is not a de Polignac number, because 21132531 - 2⁵ = 21132499 is a prime.

It is a super-2 number, since 2×21132531² = 893167732931922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21132571) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 175 + ... + 6503.

It is an arithmetic number, because the mean of its divisors is an integer number (1481220).

Almost surely, 2^21132531 is an apocalyptic number.

21132531 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21132531 is a deficient number, since it is larger than the sum of its proper divisors (14416749).

21132531 is a wasteful number, since it uses less digits than its factorization.

21132531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6395 (or 6392 counting only the distinct ones).

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

The square root of 21132531 is about 4597.0132695045. The cubic root of 21132531 is about 276.4715866455.

Adding to 21132531 its reverse (13523112), we get a palindrome (34655643).

The spelling of 21132531 in words is "twenty-one million, one hundred thirty-two thousand, five hundred thirty-one".