21227728644 has 144 divisors (see below), whose sum is σ = 59939559680. Its totient is φ = 6547353120.

The previous prime is 21227728637. The next prime is 21227728651. The reversal of 21227728644 is 44682772212.

It is an interprime number because it is at equal distance from previous prime (21227728637) and next prime (21227728651).

It is a self number, because there is not a number n which added to its sum of digits gives 21227728644.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 780759 + ... + 807489.

Almost surely, 2^21227728644 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 21227728644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29969779840).

21227728644 is an abundant number, since it is smaller than the sum of its proper divisors (38711831036).

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

21227728644 is a wasteful number, since it uses less digits than its factorization.

21227728644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26812 (or 26798 counting only the distinct ones).

The product of its digits is 602112, while the sum is 45.

The spelling of 21227728644 in words is "twenty-one billion, two hundred twenty-seven million, seven hundred twenty-eight thousand, six hundred forty-four".