21309945939 has 16 divisors (see below), whose sum is σ = 32340299040. Its totient is φ = 13860126720.

The previous prime is 21309945931. The next prime is 21309945973. The reversal of 21309945939 is 93954990312.

It is not a de Polignac number, because 21309945939 - 2³ = 21309945931 is a prime.

It is a super-2 number, since 2×21309945939² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21309945931) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9623982 + ... + 9626195.

It is an arithmetic number, because the mean of its divisors is an integer number (2021268690).

Almost surely, 2^21309945939 is an apocalyptic number.

21309945939 is a deficient number, since it is larger than the sum of its proper divisors (11030353101).

21309945939 is a wasteful number, since it uses less digits than its factorization.

21309945939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19250227 (or 19250221 counting only the distinct ones).

The product of its (nonzero) digits is 2361960, while the sum is 54.

The spelling of 21309945939 in words is "twenty-one billion, three hundred nine million, nine hundred forty-five thousand, nine hundred thirty-nine".