21978478490 has 16 divisors (see below), whose sum is σ = 39562956360. Its totient is φ = 8791014720.

The previous prime is 21978478481. The next prime is 21978478493. The reversal of 21978478490 is 9487487912.

It can be written as a sum of positive squares in 4 ways, for example, as 14070467161 + 7908011329 = 118619^2 + 88927^2 .

It is not an unprimeable number, because it can be changed into a prime (21978478493) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 401360 + ... + 452820.

Almost surely, 2^21978478490 is an apocalyptic number.

21978478490 is a deficient number, since it is larger than the sum of its proper divisors (17584477870).

21978478490 is a wasteful number, since it uses less digits than its factorization.

21978478490 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 94177.

The product of its (nonzero) digits is 8128512, while the sum is 59.

The spelling of 21978478490 in words is "twenty-one billion, nine hundred seventy-eight million, four hundred seventy-eight thousand, four hundred ninety".