21785228 has 24 divisors (see below), whose sum is σ = 40572000. Its totient is φ = 10199808.

The previous prime is 21785189. The next prime is 21785237. The reversal of 21785228 is 82258712.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 14873 + ... + 16271.

It is an arithmetic number, because the mean of its divisors is an integer number (1690500).

Almost surely, 2^21785228 is an apocalyptic number.

It is an amenable number.

21785228 is a deficient number, since it is larger than the sum of its proper divisors (18786772).

21785228 is a wasteful number, since it uses less digits than its factorization.

21785228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1649 (or 1647 counting only the distinct ones).

The product of its digits is 17920, while the sum is 35.

The square root of 21785228 is about 4667.4648365039. The cubic root of 21785228 is about 279.2891321403.

The spelling of 21785228 in words is "twenty-one million, seven hundred eighty-five thousand, two hundred twenty-eight".