21791090644 has 12 divisors (see below), whose sum is σ = 38199377664. Its totient is φ = 10876982744.

The previous prime is 21791090641. The next prime is 21791090647. The reversal of 21791090644 is 44609019712.

It is an interprime number because it is at equal distance from previous prime (21791090641) and next prime (21791090647).

It is a self number, because there is not a number n which added to its sum of digits gives 21791090644.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21791090641) 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, 4638004 + ... + 4642699.

It is an arithmetic number, because the mean of its divisors is an integer number (3183281472).

Almost surely, 2^21791090644 is an apocalyptic number.

It is an amenable number.

21791090644 is a deficient number, since it is larger than the sum of its proper divisors (16408287020).

21791090644 is a wasteful number, since it uses less digits than its factorization.

21791090644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9281294 (or 9281292 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 43.

The spelling of 21791090644 in words is "twenty-one billion, seven hundred ninety-one million, ninety thousand, six hundred forty-four".