21251644456 has 64 divisors (see below), whose sum is σ = 47163617280. Its totient is φ = 8788436160.

The previous prime is 21251644423. The next prime is 21251644471. The reversal of 21251644456 is 65444615212.

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, 130011 + ... + 243733.

It is an arithmetic number, because the mean of its divisors is an integer number (736931520).

Almost surely, 2^21251644456 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 21251644456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23581808640).

21251644456 is an abundant number, since it is smaller than the sum of its proper divisors (25911972824).

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

21251644456 is a wasteful number, since it uses less digits than its factorization.

21251644456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 113854 (or 113850 counting only the distinct ones).

The product of its digits is 230400, while the sum is 40.

It can be divided in two parts, 21251644 and 456, that added together give a square (21252100 = 4610²).

The spelling of 21251644456 in words is "twenty-one billion, two hundred fifty-one million, six hundred forty-four thousand, four hundred fifty-six".