21909843873 has 8 divisors (see below), whose sum is σ = 32459028000. Its totient is φ = 14606562564.

The previous prime is 21909843859. The next prime is 21909843887. The reversal of 21909843873 is 37834890912.

It is an interprime number because it is at equal distance from previous prime (21909843859) and next prime (21909843887).

It is not a de Polignac number, because 21909843873 - 2²⁶ = 21842735009 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21909843973) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 405737823 + ... + 405737876.

It is an arithmetic number, because the mean of its divisors is an integer number (4057378500).

Almost surely, 2^21909843873 is an apocalyptic number.

It is an amenable number.

21909843873 is a deficient number, since it is larger than the sum of its proper divisors (10549184127).

21909843873 is an equidigital number, since it uses as much as digits as its factorization.

21909843873 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 811475708 (or 811475702 counting only the distinct ones).

The product of its (nonzero) digits is 2612736, while the sum is 54.

The spelling of 21909843873 in words is "twenty-one billion, nine hundred nine million, eight hundred forty-three thousand, eight hundred seventy-three".