21978480778 has 8 divisors (see below), whose sum is σ = 33858740772. Its totient is φ = 10692233856.

The previous prime is 21978480731. The next prime is 21978480857. The reversal of 21978480778 is 87708487912.

It can be written as a sum of positive squares in 2 ways, for example, as 15807278529 + 6171202249 = 125727^2 + 78557^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 148503175 + ... + 148503322.

Almost surely, 2^21978480778 is an apocalyptic number.

21978480778 is a deficient number, since it is larger than the sum of its proper divisors (11880259994).

21978480778 is a wasteful number, since it uses less digits than its factorization.

21978480778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 297006536.

The product of its (nonzero) digits is 12644352, while the sum is 61.

The spelling of 21978480778 in words is "twenty-one billion, nine hundred seventy-eight million, four hundred eighty thousand, seven hundred seventy-eight".