21237661971 has 8 divisors (see below), whose sum is σ = 31463202960. Its totient is φ = 14158441296.

The previous prime is 21237661933. The next prime is 21237661987. The reversal of 21237661971 is 17916673212.

21237661971 is a `hidden beast` number, since 2 + 1 + 23 + 7 + 6 + 619 + 7 + 1 = 666.

It is a de Polignac number, because none of the positive numbers 2^k-21237661971 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21237661871) 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, 393290010 + ... + 393290063.

It is an arithmetic number, because the mean of its divisors is an integer number (3932900370).

Almost surely, 2^21237661971 is an apocalyptic number.

21237661971 is a deficient number, since it is larger than the sum of its proper divisors (10225540989).

21237661971 is an equidigital number, since it uses as much as digits as its factorization.

21237661971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 786580082 (or 786580076 counting only the distinct ones).

The product of its digits is 190512, while the sum is 45.

The spelling of 21237661971 in words is "twenty-one billion, two hundred thirty-seven million, six hundred sixty-one thousand, nine hundred seventy-one".