21643663616 has 36 divisors (see below), whose sum is σ = 43213430400. Its totient is φ = 10819164672.

The previous prime is 21643663609. The next prime is 21643663633. The reversal of 21643663616 is 61636634612.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1405205 + ... + 1420523.

Almost surely, 2^21643663616 is an apocalyptic number.

It is an amenable number.

21643663616 is a deficient number, since it is larger than the sum of its proper divisors (21569766784).

21643663616 is an equidigital number, since it uses as much as digits as its factorization.

21643663616 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20854 (or 20840 counting only the distinct ones).

The product of its digits is 559872, while the sum is 44.

The spelling of 21643663616 in words is "twenty-one billion, six hundred forty-three million, six hundred sixty-three thousand, six hundred sixteen".