16561778976 has 72 divisors (see below), whose sum is σ = 48370497084. Its totient is φ = 5371384320.

The previous prime is 16561778969. The next prime is 16561779007. The reversal of 16561778976 is 67987716561.

16561778976 is a `hidden beast` number, since 1 + 6 + 5 + 617 + 7 + 8 + 9 + 7 + 6 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 16378880400 + 182898576 = 127980^2 + 13524^2 .

It is a tau number, because it is divible by the number of its divisors (72).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 766455 + ... + 787766.

Almost surely, 2^16561778976 is an apocalyptic number.

16561778976 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

16561778976 is an abundant number, since it is smaller than the sum of its proper divisors (31808718108).

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

16561778976 is a wasteful number, since it uses less digits than its factorization.

16561778976 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1554274 (or 1554263 counting only the distinct ones).

The product of its digits is 26671680, while the sum is 63.

The spelling of 16561778976 in words is "sixteen billion, five hundred sixty-one million, seven hundred seventy-eight thousand, nine hundred seventy-six".