21006440939 has 16 divisors (see below), whose sum is σ = 23546570496. Its totient is φ = 18571874400.

The previous prime is 21006440927. The next prime is 21006440947. The reversal of 21006440939 is 93904460012.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21006440939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21006440909) 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, 944234 + ... + 966224.

It is an arithmetic number, because the mean of its divisors is an integer number (1471660656).

Almost surely, 2^21006440939 is an apocalyptic number.

21006440939 is a deficient number, since it is larger than the sum of its proper divisors (2540129557).

21006440939 is a wasteful number, since it uses less digits than its factorization.

21006440939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24386.

The product of its (nonzero) digits is 46656, while the sum is 38.

The spelling of 21006440939 in words is "twenty-one billion, six million, four hundred forty thousand, nine hundred thirty-nine".