21605628 has 24 divisors (see below), whose sum is σ = 54996480. Its totient is φ = 6547120.

The previous prime is 21605627. The next prime is 21605659. The reversal of 21605628 is 82650612.

It is a super-2 number, since 2×21605628² = 933606322548768, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21605595 and 21605604.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21605627) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 81708 + ... + 81971.

It is an arithmetic number, because the mean of its divisors is an integer number (2291520).

Almost surely, 2^21605628 is an apocalyptic number.

It is an amenable number.

21605628 is an abundant number, since it is smaller than the sum of its proper divisors (33390852).

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

21605628 is a wasteful number, since it uses less digits than its factorization.

21605628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 163697 (or 163695 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 30.

The square root of 21605628 is about 4648.1854524104. The cubic root of 21605628 is about 278.5195157515.

The spelling of 21605628 in words is "twenty-one million, six hundred five thousand, six hundred twenty-eight".