21358728 has 48 divisors (see below), whose sum is σ = 59994480. Its totient is φ = 7118928.

The previous prime is 21358699. The next prime is 21358739. The reversal of 21358728 is 82785312.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21358692 and 21358701.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3550 + ... + 7437.

It is an arithmetic number, because the mean of its divisors is an integer number (1249885).

Almost surely, 2^21358728 is an apocalyptic number.

It is an amenable number.

21358728 is an abundant number, since it is smaller than the sum of its proper divisors (38635752).

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

21358728 is a wasteful number, since it uses less digits than its factorization.

21358728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11008 (or 10992 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 21358728 is about 4621.5503892092. The cubic root of 21358728 is about 277.4545140932.

The spelling of 21358728 in words is "twenty-one million, three hundred fifty-eight thousand, seven hundred twenty-eight".