21994882728 has 256 divisors, whose sum is σ = 71170444800. Its totient is φ = 5508034560.

The previous prime is 21994882691. The next prime is 21994882729. The reversal of 21994882728 is 82728849912.

It is not an unprimeable number, because it can be changed into a prime (21994882729) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 3860650 + ... + 3866342.

It is an arithmetic number, because the mean of its divisors is an integer number (278009550).

Almost surely, 2^21994882728 is an apocalyptic number.

21994882728 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21994882728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35585222400).

21994882728 is an abundant number, since it is smaller than the sum of its proper divisors (49175562072).

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

21994882728 is a wasteful number, since it uses less digits than its factorization.

21994882728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5812 (or 5808 counting only the distinct ones).

The product of its digits is 9289728, while the sum is 60.

The spelling of 21994882728 in words is "twenty-one billion, nine hundred ninety-four million, eight hundred eighty-two thousand, seven hundred twenty-eight".