21368539 has 2 divisors, whose sum is σ = 21368540. Its totient is φ = 21368538.

The previous prime is 21368531. The next prime is 21368569. The reversal of 21368539 is 93586312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21368539 - 2³ = 21368531 is a prime.

It is a super-2 number, since 2×21368539² = 913228917989042, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21368498 and 21368507.

It is not a weakly prime, because it can be changed into another prime (21368531) 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, 10684269 + 10684270.

It is an arithmetic number, because the mean of its divisors is an integer number (10684270).

Almost surely, 2^21368539 is an apocalyptic number.

21368539 is a deficient number, since it is larger than the sum of its proper divisors (1).

21368539 is an equidigital number, since it uses as much as digits as its factorization.

21368539 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 38880, while the sum is 37.

The square root of 21368539 is about 4622.6117076821. The cubic root of 21368539 is about 277.4969899303.

The spelling of 21368539 in words is "twenty-one million, three hundred sixty-eight thousand, five hundred thirty-nine".