21902728 has 8 divisors (see below), whose sum is σ = 41067630. Its totient is φ = 10951360.

The previous prime is 21902723. The next prime is 21902729. The reversal of 21902728 is 82720912.

It can be written as a sum of positive squares in only one way, i.e., 21883684 + 19044 = 4678^2 + 138^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a self number, because there is not a number n which added to its sum of digits gives 21902728.

It is not an unprimeable number, because it can be changed into a prime (21902723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1368913 + ... + 1368928.

Almost surely, 2^21902728 is an apocalyptic number.

It is an amenable number.

21902728 is a deficient number, since it is larger than the sum of its proper divisors (19164902).

21902728 is a wasteful number, since it uses less digits than its factorization.

21902728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2737847 (or 2737843 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 21902728 is about 4680.0350426038. The cubic root of 21902728 is about 279.7903532727.

The spelling of 21902728 in words is "twenty-one million, nine hundred two thousand, seven hundred twenty-eight".