21064531 has 4 divisors (see below), whose sum is σ = 21744064. Its totient is φ = 20385000.

The previous prime is 21064523. The next prime is 21064553. The reversal of 21064531 is 13546012.

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 21064531 - 2³ = 21064523 is a prime.

It is a super-2 number, since 2×21064531² = 887428932499922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21064591) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 339720 + ... + 339781.

It is an arithmetic number, because the mean of its divisors is an integer number (5436016).

Almost surely, 2^21064531 is an apocalyptic number.

21064531 is a deficient number, since it is larger than the sum of its proper divisors (679533).

21064531 is an equidigital number, since it uses as much as digits as its factorization.

21064531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 679532.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21064531 is about 4589.6112035771. The cubic root of 21064531 is about 276.1747257080.

The spelling of 21064531 in words is "twenty-one million, sixty-four thousand, five hundred thirty-one".