21244640256 has 352 divisors, whose sum is σ = 74244853760. Its totient is φ = 5872435200.

The previous prime is 21244640233. The next prime is 21244640267. The reversal of 21244640256 is 65204644212.

21244640256 is a `hidden beast` number, since 2 + 1 + 2 + 4 + 4 + 640 + 2 + 5 + 6 = 666.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21244640256.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 5997846 + ... + 6001386.

It is an arithmetic number, because the mean of its divisors is an integer number (210922880).

Almost surely, 2^21244640256 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 21244640256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37122426880).

21244640256 is an abundant number, since it is smaller than the sum of its proper divisors (53000213504).

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

21244640256 is a wasteful number, since it uses less digits than its factorization.

21244640256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3608 (or 3584 counting only the distinct ones).

The product of its (nonzero) digits is 92160, while the sum is 36.

The spelling of 21244640256 in words is "twenty-one billion, two hundred forty-four million, six hundred forty thousand, two hundred fifty-six".