21639586816 has 33 divisors (see below), whose sum is σ = 43267453329. Its totient is φ = 10817439744.

The previous prime is 21639586781. The next prime is 21639586817. The reversal of 21639586816 is 61868593612.

The square root of 21639586816 is 147104.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 1561830400 + 20077756416 = 39520^2 + 141696^2 .

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21639586817) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 4705030 + ... + 4709626.

Almost surely, 2^21639586816 is an apocalyptic number.

21639586816 is the 147104-th square number.

It is an amenable number.

21639586816 is a deficient number, since it is larger than the sum of its proper divisors (21627866513).

21639586816 is an frugal number, since it uses more digits than its factorization.

21639586816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9214 (or 4599 counting only the distinct ones).

The product of its digits is 3732480, while the sum is 55.

The spelling of 21639586816 in words is "twenty-one billion, six hundred thirty-nine million, five hundred eighty-six thousand, eight hundred sixteen".