21978728669376 has 84 divisors (see below), whose sum is σ = 63757070227032. Its totient is φ = 7237974887424.

The previous prime is 21978728669363. The next prime is 21978728669377. The reversal of 21978728669376 is 67396682787912.

It is a happy number.

21978728669376 is a `hidden beast` number, since 2 + 1 + 97 + 87 + 2 + 86 + 6 + 9 + 376 = 666.

It is a Smith number, since the sum of its digits (81) coincides with the sum of the digits of its prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 21978728669295 and 21978728669304.

It is not an unprimeable number, because it can be changed into a prime (21978728669377) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 229816741 + ... + 229912356.

It is an arithmetic number, because the mean of its divisors is an integer number (759012740798).

Almost surely, 2^{21978728669376} is an apocalyptic number.

It is an amenable number.

21978728669376 is an abundant number, since it is smaller than the sum of its proper divisors (41778341557656).

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

21978728669376 is a wasteful number, since it uses less digits than its factorization.

21978728669376 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 459729198 (or 459729185 counting only the distinct ones).

The product of its digits is 4608866304, while the sum is 81.

The spelling of 21978728669376 in words is "twenty-one trillion, nine hundred seventy-eight billion, seven hundred twenty-eight million, six hundred sixty-nine thousand, three hundred seventy-six".