21643724907 has 64 divisors (see below), whose sum is σ = 36918400000. Its totient is φ = 12276126720.

The previous prime is 21643724857. The next prime is 21643724917. The reversal of 21643724907 is 70942734612.

It is not a de Polignac number, because 21643724907 - 2¹⁰ = 21643723883 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21643724917) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 17328219 + ... + 17329467.

It is an arithmetic number, because the mean of its divisors is an integer number (576850000).

Almost surely, 2^21643724907 is an apocalyptic number.

21643724907 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21643724907 is a deficient number, since it is larger than the sum of its proper divisors (15274675093).

21643724907 is a wasteful number, since it uses less digits than its factorization.

21643724907 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1873 (or 1867 counting only the distinct ones).

The product of its (nonzero) digits is 508032, while the sum is 45.

The spelling of 21643724907 in words is "twenty-one billion, six hundred forty-three million, seven hundred twenty-four thousand, nine hundred seven".