21918377531 has 8 divisors (see below), whose sum is σ = 22315670880. Its totient is φ = 21523707072.

The previous prime is 21918377489. The next prime is 21918377557. The reversal of 21918377531 is 13577381912.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21918377531 - 2²² = 21914183227 is a prime.

It is a super-2 number, since 2×21918377531² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21918377581) 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, 638855 + ... + 672288.

It is an arithmetic number, because the mean of its divisors is an integer number (2789458860).

Almost surely, 2^21918377531 is an apocalyptic number.

21918377531 is a deficient number, since it is larger than the sum of its proper divisors (397293349).

21918377531 is a wasteful number, since it uses less digits than its factorization.

21918377531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1311445.

The product of its digits is 317520, while the sum is 47.

The spelling of 21918377531 in words is "twenty-one billion, nine hundred eighteen million, three hundred seventy-seven thousand, five hundred thirty-one".