21256123392 has 264 divisors, whose sum is σ = 70600473216. Its totient is φ = 6033752064.

The previous prime is 21256123337. The next prime is 21256123423. The reversal of 21256123392 is 29332165212.

21256123392 is a `hidden beast` number, since 2 + 1 + 2 + 5 + 612 + 3 + 39 + 2 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 10772518 + ... + 10774490.

Almost surely, 2^21256123392 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 21256123392, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35300236608).

21256123392 is an abundant number, since it is smaller than the sum of its proper divisors (49344349824).

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

21256123392 is a wasteful number, since it uses less digits than its factorization.

21256123392 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2173 (or 2152 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The spelling of 21256123392 in words is "twenty-one billion, two hundred fifty-six million, one hundred twenty-three thousand, three hundred ninety-two".