21239507 has 2 divisors, whose sum is σ = 21239508. Its totient is φ = 21239506.

The previous prime is 21239501. The next prime is 21239551. The reversal of 21239507 is 70593212.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21239507 is a prime.

It is a super-2 number, since 2×21239507² = 902233315206098, which contains 22 as substring.

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 21239507.

It is not a weakly prime, because it can be changed into another prime (21239501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10619753 + 10619754.

It is an arithmetic number, because the mean of its divisors is an integer number (10619754).

Almost surely, 2^21239507 is an apocalyptic number.

21239507 is a deficient number, since it is larger than the sum of its proper divisors (1).

21239507 is an equidigital number, since it uses as much as digits as its factorization.

21239507 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3780, while the sum is 29.

The square root of 21239507 is about 4608.6339624665. The cubic root of 21239507 is about 276.9373150304.

The spelling of 21239507 in words is "twenty-one million, two hundred thirty-nine thousand, five hundred seven".