21690631847 has 4 divisors (see below), whose sum is σ = 21996133776. Its totient is φ = 21385129920.

The previous prime is 21690631777. The next prime is 21690631849. The reversal of 21690631847 is 74813609612.

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 21690631847 - 2²⁸ = 21422196391 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21690631849) 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, 152750858 + ... + 152750999.

It is an arithmetic number, because the mean of its divisors is an integer number (5499033444).

Almost surely, 2^21690631847 is an apocalyptic number.

21690631847 is a deficient number, since it is larger than the sum of its proper divisors (305501929).

21690631847 is an equidigital number, since it uses as much as digits as its factorization.

21690631847 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 305501928.

The product of its (nonzero) digits is 435456, while the sum is 47.

The spelling of 21690631847 in words is "twenty-one billion, six hundred ninety million, six hundred thirty-one thousand, eight hundred forty-seven".