21780005256 has 96 divisors (see below), whose sum is σ = 61068945600. Its totient is φ = 7004215680.

The previous prime is 21780005239. The next prime is 21780005279. The reversal of 21780005256 is 65250008712.

It is a happy number.

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 21780005256.

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, 3352171 + ... + 3358661.

It is an arithmetic number, because the mean of its divisors is an integer number (636134850).

Almost surely, 2^21780005256 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 21780005256, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30534472800).

21780005256 is an abundant number, since it is smaller than the sum of its proper divisors (39288940344).

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

21780005256 is a wasteful number, since it uses less digits than its factorization.

21780005256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8139 (or 8132 counting only the distinct ones).

The product of its (nonzero) digits is 33600, while the sum is 36.

The spelling of 21780005256 in words is "twenty-one billion, seven hundred eighty million, five thousand, two hundred fifty-six".