21338531 has 2 divisors, whose sum is σ = 21338532. Its totient is φ = 21338530.

The previous prime is 21338521. The next prime is 21338533. The reversal of 21338531 is 13583312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21338531 - 2⁶ = 21338467 is a prime.

It is a super-2 number, since 2×21338531² = 910665810475922, which contains 22 as substring.

Together with 21338533, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21338531.

It is not a weakly prime, because it can be changed into another prime (21338533) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10669265 + 10669266.

It is an arithmetic number, because the mean of its divisors is an integer number (10669266).

Almost surely, 2^21338531 is an apocalyptic number.

21338531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21338531 is an equidigital number, since it uses as much as digits as its factorization.

21338531 is an evil number, because the sum of its binary digits is even.

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

The square root of 21338531 is about 4619.3647831710. The cubic root of 21338531 is about 277.3670320411.

The spelling of 21338531 in words is "twenty-one million, three hundred thirty-eight thousand, five hundred thirty-one".