20661388456 has 16 divisors (see below), whose sum is σ = 38744480340. Its totient is φ = 10329527040.

The previous prime is 20661388439. The next prime is 20661388469. The reversal of 20661388456 is 65488316602.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 18595685956 + 2065702500 = 136366^2 + 45450^2 .

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, 68235 + ... + 214426.

Almost surely, 2^20661388456 is an apocalyptic number.

It is an amenable number.

20661388456 is a deficient number, since it is larger than the sum of its proper divisors (18083091884).

20661388456 is a wasteful number, since it uses less digits than its factorization.

20661388456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 291804 (or 291800 counting only the distinct ones).

The product of its (nonzero) digits is 1658880, while the sum is 49.

The spelling of 20661388456 in words is "twenty billion, six hundred sixty-one million, three hundred eighty-eight thousand, four hundred fifty-six".