21437531 has 2 divisors, whose sum is σ = 21437532. Its totient is φ = 21437530.

The previous prime is 21437501. The next prime is 21437573. The reversal of 21437531 is 13573412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21437531 - 2²² = 17243227 is a prime.

It is a super-2 number, since 2×21437531² = 919135470751922, 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 21437531.

It is not a weakly prime, because it can be changed into another prime (21437501) 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 as a sum of consecutive naturals, namely, 10718765 + 10718766.

It is an arithmetic number, because the mean of its divisors is an integer number (10718766).

Almost surely, 2^21437531 is an apocalyptic number.

21437531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21437531 is an equidigital number, since it uses as much as digits as its factorization.

21437531 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 21437531 is about 4630.0681420472. The cubic root of 21437531 is about 277.7953179976.

The spelling of 21437531 in words is "twenty-one million, four hundred thirty-seven thousand, five hundred thirty-one".