21473531 has 2 divisors, whose sum is σ = 21473532. Its totient is φ = 21473530.

The previous prime is 21473527. The next prime is 21473549. The reversal of 21473531 is 13537412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21473531 - 2² = 21473527 is a prime.

It is a super-2 number, since 2×21473531² = 922225067215922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21473531.

It is not a weakly prime, because it can be changed into another prime (21472531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10736765 + 10736766.

It is an arithmetic number, because the mean of its divisors is an integer number (10736766).

Almost surely, 2^21473531 is an apocalyptic number.

21473531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21473531 is an equidigital number, since it uses as much as digits as its factorization.

21473531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2520, while the sum is 26.

The square root of 21473531 is about 4633.9541430618. The cubic root of 21473531 is about 277.9507313962.

The spelling of 21473531 in words is "twenty-one million, four hundred seventy-three thousand, five hundred thirty-one".