21502939 has 2 divisors, whose sum is σ = 21502940. Its totient is φ = 21502938.

The previous prime is 21502879. The next prime is 21502961. The reversal of 21502939 is 93920512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21502939 - 2²³ = 13114331 is a prime.

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 21502939.

It is not a weakly prime, because it can be changed into another prime (21502969) 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, 10751469 + 10751470.

It is an arithmetic number, because the mean of its divisors is an integer number (10751470).

Almost surely, 2^21502939 is an apocalyptic number.

21502939 is a deficient number, since it is larger than the sum of its proper divisors (1).

21502939 is an equidigital number, since it uses as much as digits as its factorization.

21502939 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4860, while the sum is 31.

The square root of 21502939 is about 4637.1261574385. The cubic root of 21502939 is about 278.0775580233.

The spelling of 21502939 in words is "twenty-one million, five hundred two thousand, nine hundred thirty-nine".