21093939 has 10 divisors (see below), whose sum is σ = 31510820. Its totient is φ = 14062572.

The previous prime is 21093913. The next prime is 21093997. The reversal of 21093939 is 93939012.

It is not a de Polignac number, because 21093939 - 2⁵ = 21093907 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21093239) 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 in 9 ways as a sum of consecutive naturals, for example, 130129 + ... + 130290.

It is an arithmetic number, because the mean of its divisors is an integer number (3151082).

Almost surely, 2^21093939 is an apocalyptic number.

21093939 is a deficient number, since it is larger than the sum of its proper divisors (10416881).

21093939 is an equidigital number, since it uses as much as digits as its factorization.

21093939 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 260431 (or 260422 counting only the distinct ones).

The product of its (nonzero) digits is 13122, while the sum is 36.

The square root of 21093939 is about 4592.8138433862. The cubic root of 21093939 is about 276.3031876186.

It can be divided in two parts, 210 and 93939, that added together give a palindrome (94149).

The spelling of 21093939 in words is "twenty-one million, ninety-three thousand, nine hundred thirty-nine".