21131638667 has 4 divisors (see below), whose sum is σ = 21139905456. Its totient is φ = 21123371880.

The previous prime is 21131638657. The next prime is 21131638681. The reversal of 21131638667 is 76683613112.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21131638667 - 2²² = 21127444363 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21131638637) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4129559 + ... + 4134672.

It is an arithmetic number, because the mean of its divisors is an integer number (5284976364).

Almost surely, 2^21131638667 is an apocalyptic number.

21131638667 is a deficient number, since it is larger than the sum of its proper divisors (8266789).

21131638667 is an equidigital number, since it uses as much as digits as its factorization.

21131638667 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8266788.

The product of its digits is 217728, while the sum is 44.

The spelling of 21131638667 in words is "twenty-one billion, one hundred thirty-one million, six hundred thirty-eight thousand, six hundred sixty-seven".