21131523531 has 24 divisors (see below), whose sum is σ = 32233194240. Its totient is φ = 13303278000.

The previous prime is 21131523503. The next prime is 21131523547. The reversal of 21131523531 is 13532513112.

21131523531 is a `hidden beast` number, since 2 + 1 + 131 + 523 + 5 + 3 + 1 = 666.

It is not a de Polignac number, because 21131523531 - 2⁵ = 21131523499 is a prime.

It is a super-2 number, since 2×21131523531² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21131523495 and 21131523504.

It is not an unprimeable number, because it can be changed into a prime (21131523551) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 145495 + ... + 251856.

It is an arithmetic number, because the mean of its divisors is an integer number (1343049760).

Almost surely, 2^21131523531 is an apocalyptic number.

21131523531 is a deficient number, since it is larger than the sum of its proper divisors (11101670709).

21131523531 is a wasteful number, since it uses less digits than its factorization.

21131523531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 397687 (or 397684 counting only the distinct ones).

The product of its digits is 2700, while the sum is 27.

The spelling of 21131523531 in words is "twenty-one billion, one hundred thirty-one million, five hundred twenty-three thousand, five hundred thirty-one".