21455730 has 24 divisors (see below), whose sum is σ = 55785132. Its totient is φ = 5721504.

The previous prime is 21455729. The next prime is 21455743. The reversal of 21455730 is 3755412.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 19105641 + 2350089 = 4371^2 + 1533^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21455694 and 21455703.

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, 119109 + ... + 119288.

Almost surely, 2^21455730 is an apocalyptic number.

21455730 is an abundant number, since it is smaller than the sum of its proper divisors (34329402).

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

21455730 is a wasteful number, since it uses less digits than its factorization.

21455730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 238410 (or 238407 counting only the distinct ones).

The product of its (nonzero) digits is 4200, while the sum is 27.

The square root of 21455730 is about 4632.0330309703. The cubic root of 21455730 is about 277.8739055154.

It can be divided in two parts, 2145 and 5730, that added together give a triangular number (7875 = T₁₂₅).

The spelling of 21455730 in words is "twenty-one million, four hundred fifty-five thousand, seven hundred thirty".