21978077472 has 144 divisors (see below), whose sum is σ = 68411980728. Its totient is φ = 6651555840.

The previous prime is 21978077449. The next prime is 21978077497. The reversal of 21978077472 is 27477087912.

21978077472 is a `hidden beast` number, since 2 + 1 + 97 + 80 + 7 + 7 + 472 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 14622613776 + 7355463696 = 120924^2 + 85764^2 .

It is a tau number, because it is divible by the number of its divisors (144).

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 180268 + ... + 276500.

Almost surely, 2^21978077472 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21978077472, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34205990364).

21978077472 is an abundant number, since it is smaller than the sum of its proper divisors (46433903256).

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

21978077472 is a wasteful number, since it uses less digits than its factorization.

21978077472 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96323 (or 96312 counting only the distinct ones).

The product of its (nonzero) digits is 2765952, while the sum is 54.

The spelling of 21978077472 in words is "twenty-one billion, nine hundred seventy-eight million, seventy-seven thousand, four hundred seventy-two".