21675220 has 24 divisors (see below), whose sum is σ = 52020864. Its totient is φ = 7431456.

The previous prime is 21675211. The next prime is 21675239. The reversal of 21675220 is 2257612.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 77272 + ... + 77551.

It is an arithmetic number, because the mean of its divisors is an integer number (2167536).

Almost surely, 2^21675220 is an apocalyptic number.

21675220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21675220 is an abundant number, since it is smaller than the sum of its proper divisors (30345644).

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

21675220 is a wasteful number, since it uses less digits than its factorization.

21675220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 154839 (or 154837 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 21675220 is about 4655.6653659815. The cubic root of 21675220 is about 278.8182335458.

It can be divided in two parts, 216752 and 20, that multiplied together give a triangular number (4335040 = T₂₉₄₄).

The spelling of 21675220 in words is "twenty-one million, six hundred seventy-five thousand, two hundred twenty".