21391907955 has 64 divisors (see below), whose sum is σ = 38330910720. Its totient is φ = 10099814400.

The previous prime is 21391907951. The next prime is 21391907963. The reversal of 21391907955 is 55970919312.

It is not a de Polignac number, because 21391907955 - 2² = 21391907951 is a prime.

It is a super-2 number, since 2×21391907955² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21391907898 and 21391907907.

It is not an unprimeable number, because it can be changed into a prime (21391907951) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 940315 + ... + 962795.

It is an arithmetic number, because the mean of its divisors is an integer number (598920480).

Almost surely, 2^21391907955 is an apocalyptic number.

21391907955 is a deficient number, since it is larger than the sum of its proper divisors (16939002765).

21391907955 is a wasteful number, since it uses less digits than its factorization.

21391907955 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22652.

The product of its (nonzero) digits is 765450, while the sum is 51.

The spelling of 21391907955 in words is "twenty-one billion, three hundred ninety-one million, nine hundred seven thousand, nine hundred fifty-five".