20993691664 has 135 divisors (see below), whose sum is σ = 46472299671. Its totient is φ = 9180357120.

The previous prime is 20993691643. The next prime is 20993691683. The reversal of 20993691664 is 46619639902.

The square root of 20993691664 is 144892.

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

It can be written as a sum of positive squares in 4 ways, for example, as 317552400 + 20676139264 = 17820^2 + 143792^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 235884132 + ... + 235884220.

Almost surely, 2^20993691664 is an apocalyptic number.

20993691664 is the 144892-nd square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20993691664

20993691664 is an abundant number, since it is smaller than the sum of its proper divisors (25478608007).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20993691664 is an equidigital number, since it uses as much as digits as its factorization.

20993691664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 282 (or 139 counting only the distinct ones).

The product of its (nonzero) digits is 3779136, while the sum is 55.

The spelling of 20993691664 in words is "twenty billion, nine hundred ninety-three million, six hundred ninety-one thousand, six hundred sixty-four".