21509874 has 28 divisors (see below), whose sum is σ = 48378366. Its totient is φ = 7169472.

The previous prime is 21509867. The next prime is 21509897. The reversal of 21509874 is 47890512.

It can be written as a sum of positive squares in only one way, i.e., 18429849 + 3080025 = 4293^2 + 1755^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 5919 + ... + 8834.

Almost surely, 2^21509874 is an apocalyptic number.

21509874 is an abundant number, since it is smaller than the sum of its proper divisors (26868492).

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

21509874 is an equidigital number, since it uses as much as digits as its factorization.

21509874 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14773 (or 14758 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 21509874 is about 4637.8738663314. The cubic root of 21509874 is about 278.1074494501.

The spelling of 21509874 in words is "twenty-one million, five hundred nine thousand, eight hundred seventy-four".