21293939 has 2 divisors, whose sum is σ = 21293940. Its totient is φ = 21293938.

The previous prime is 21293903. The next prime is 21293947. The reversal of 21293939 is 93939212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21293939 - 2¹² = 21289843 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21293959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10646969 + 10646970.

It is an arithmetic number, because the mean of its divisors is an integer number (10646970).

Almost surely, 2^21293939 is an apocalyptic number.

21293939 is a deficient number, since it is larger than the sum of its proper divisors (1).

21293939 is an equidigital number, since it uses as much as digits as its factorization.

21293939 is an evil number, because the sum of its binary digits is even.

The product of its digits is 26244, while the sum is 38.

The square root of 21293939 is about 4614.5356212733. The cubic root of 21293939 is about 277.1736888933.

The spelling of 21293939 in words is "twenty-one million, two hundred ninety-three thousand, nine hundred thirty-nine".