21368531 has 2 divisors, whose sum is σ = 21368532. Its totient is φ = 21368530.

The previous prime is 21368527. The next prime is 21368539. The reversal of 21368531 is 13586312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21368531 - 2² = 21368527 is a prime.

It is a super-2 number, since 2×21368531² = 913228234195922, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21368494 and 21368503.

It is not a weakly prime, because it can be changed into another prime (21368539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10684265 + 10684266.

It is an arithmetic number, because the mean of its divisors is an integer number (10684266).

Almost surely, 2^21368531 is an apocalyptic number.

21368531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21368531 is an equidigital number, since it uses as much as digits as its factorization.

21368531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 29.

The square root of 21368531 is about 4622.6108423704. The cubic root of 21368531 is about 277.4969553003.

The spelling of 21368531 in words is "twenty-one million, three hundred sixty-eight thousand, five hundred thirty-one".