21266531 has 16 divisors (see below), whose sum is σ = 25202688. Its totient is φ = 17690400.

The previous prime is 21266521. The next prime is 21266551. The reversal of 21266531 is 13566212.

It is not a de Polignac number, because 21266531 - 2¹⁸ = 21004387 is a prime.

It is a super-2 number, since 2×21266531² = 904530681547922, which contains 22 as substring.

It is a Smith number, since the sum of its digits (26) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21266531.

It is not an unprimeable number, because it can be changed into a prime (21266521) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17576 + ... + 18746.

It is an arithmetic number, because the mean of its divisors is an integer number (1575168).

Almost surely, 2^21266531 is an apocalyptic number.

21266531 is a deficient number, since it is larger than the sum of its proper divisors (3936157).

21266531 is a wasteful number, since it uses less digits than its factorization.

21266531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1322.

The product of its digits is 2160, while the sum is 26.

The square root of 21266531 is about 4611.5649187667. The cubic root of 21266531 is about 277.0547186058.

The spelling of 21266531 in words is "twenty-one million, two hundred sixty-six thousand, five hundred thirty-one".