21500730 has 24 divisors (see below), whose sum is σ = 55902132. Its totient is φ = 5733504.

The previous prime is 21500711. The next prime is 21500741. The reversal of 21500730 is 3700512.

It can be written as a sum of positive squares in 2 ways, for example, as 21316689 + 184041 = 4617^2 + 429^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 119359 + ... + 119538.

Almost surely, 2^21500730 is an apocalyptic number.

21500730 is an abundant number, since it is smaller than the sum of its proper divisors (34401402).

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

21500730 is a wasteful number, since it uses less digits than its factorization.

21500730 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 238910 (or 238907 counting only the distinct ones).

The product of its (nonzero) digits is 210, while the sum is 18.

The square root of 21500730 is about 4636.8879650041. The cubic root of 21500730 is about 278.0680353814.

The spelling of 21500730 in words is "twenty-one million, five hundred thousand, seven hundred thirty".