21156730 has 24 divisors (see below), whose sum is σ = 44300628. Its totient is φ = 7253568.

The previous prime is 21156719. The next prime is 21156743. The reversal of 21156730 is 3765112.

It can be written as a sum of positive squares in 2 ways, for example, as 21150801 + 5929 = 4599^2 + 77^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21156695 and 21156704.

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 11 ways as a sum of consecutive naturals, for example, 21099 + ... + 22078.

Almost surely, 2^21156730 is an apocalyptic number.

21156730 is an abundant number, since it is smaller than the sum of its proper divisors (23143898).

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

21156730 is a wasteful number, since it uses less digits than its factorization.

21156730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43198 (or 43191 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 21156730 is about 4599.6445514844. The cubic root of 21156730 is about 276.5770761998.

The spelling of 21156730 in words is "twenty-one million, one hundred fifty-six thousand, seven hundred thirty".