21684528 has 30 divisors (see below), whose sum is σ = 60686964. Its totient is φ = 7228128.

The previous prime is 21684527. The next prime is 21684557. The reversal of 21684528 is 82548612.

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 = 21684492 and 21684501.

It is not an unprimeable number, because it can be changed into a prime (21684521) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 75150 + ... + 75437.

Almost surely, 2^21684528 is an apocalyptic number.

It is an amenable number.

21684528 is an abundant number, since it is smaller than the sum of its proper divisors (39002436).

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

21684528 is a wasteful number, since it uses less digits than its factorization.

21684528 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 150601 (or 150592 counting only the distinct ones).

The product of its digits is 30720, while the sum is 36.

The square root of 21684528 is about 4656.6649009780. The cubic root of 21684528 is about 278.8581388496.

It can be divided in two parts, 2 and 1684528, that added together give a triangular number (1684530 = T₁₈₃₅).

The spelling of 21684528 in words is "twenty-one million, six hundred eighty-four thousand, five hundred twenty-eight".