21009869939 has 2 divisors, whose sum is σ = 21009869940. Its totient is φ = 21009869938.

The previous prime is 21009869921. The next prime is 21009869977. The reversal of 21009869939 is 93996890012.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21009869939 is a prime.

It is not a weakly prime, because it can be changed into another prime (21009869999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504934969 + 10504934970.

It is an arithmetic number, because the mean of its divisors is an integer number (10504934970).

Almost surely, 2^21009869939 is an apocalyptic number.

21009869939 is a deficient number, since it is larger than the sum of its proper divisors (1).

21009869939 is an equidigital number, since it uses as much as digits as its factorization.

21009869939 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1889568, while the sum is 56.

The spelling of 21009869939 in words is "twenty-one billion, nine million, eight hundred sixty-nine thousand, nine hundred thirty-nine".