21390904278 has 40 divisors (see below), whose sum is σ = 48588093048. Its totient is φ = 7032622176.

The previous prime is 21390904267. The next prime is 21390904289. The reversal of 21390904278 is 87240909312.

21390904278 is a `hidden beast` number, since 2 + 139 + 0 + 90 + 427 + 8 = 666.

It is an interprime number because it is at equal distance from previous prime (21390904267) and next prime (21390904289).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 892576 + ... + 916227.

Almost surely, 2^21390904278 is an apocalyptic number.

21390904278 is an abundant number, since it is smaller than the sum of its proper divisors (27197188770).

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

21390904278 is a wasteful number, since it uses less digits than its factorization.

21390904278 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1808890 (or 1808881 counting only the distinct ones).

The product of its (nonzero) digits is 217728, while the sum is 45.

The spelling of 21390904278 in words is "twenty-one billion, three hundred ninety million, nine hundred four thousand, two hundred seventy-eight".