21728658 has 24 divisors (see below), whose sum is σ = 50553072. Its totient is φ = 6208104.

The previous prime is 21728633. The next prime is 21728659. The reversal of 21728658 is 85682712.

It is not an unprimeable number, because it can be changed into a prime (21728659) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 36660 + ... + 37247.

It is an arithmetic number, because the mean of its divisors is an integer number (2106378).

Almost surely, 2^21728658 is an apocalyptic number.

21728658 is an abundant number, since it is smaller than the sum of its proper divisors (28824414).

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

21728658 is a wasteful number, since it uses less digits than its factorization.

21728658 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73926 (or 73919 counting only the distinct ones).

The product of its digits is 53760, while the sum is 39.

The square root of 21728658 is about 4661.4008624018. The cubic root of 21728658 is about 279.0471779522.

The spelling of 21728658 in words is "twenty-one million, seven hundred twenty-eight thousand, six hundred fifty-eight".