21256645436 has 48 divisors (see below), whose sum is σ = 42837258240. Its totient is φ = 9142195200.

The previous prime is 21256645381. The next prime is 21256645477. The reversal of 21256645436 is 63454665212.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29756 + ... + 208323.

It is an arithmetic number, because the mean of its divisors is an integer number (892442880).

Almost surely, 2^21256645436 is an apocalyptic number.

21256645436 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21256645436 is an abundant number, since it is smaller than the sum of its proper divisors (21580612804).

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

21256645436 is a wasteful number, since it uses less digits than its factorization.

21256645436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 238214 (or 238212 counting only the distinct ones).

The product of its digits is 1036800, while the sum is 44.

The spelling of 21256645436 in words is "twenty-one billion, two hundred fifty-six million, six hundred forty-five thousand, four hundred thirty-six".