21530404 has 18 divisors (see below), whose sum is σ = 43830150. Its totient is φ = 9227232.

The previous prime is 21530393. The next prime is 21530413. The reversal of 21530404 is 40403512.

It can be written as a sum of positive squares in only one way, i.e., 14077504 + 7452900 = 3752^2 + 2730^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 54729 + ... + 55120.

Almost surely, 2^21530404 is an apocalyptic number.

It is an amenable number.

21530404 is an abundant number, since it is smaller than the sum of its proper divisors (22299746).

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

21530404 is a wasteful number, since it uses less digits than its factorization.

21530404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 109867 (or 109858 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21530404 is about 4640.0866371222. The cubic root of 21530404 is about 278.1959007728.

Adding to 21530404 its reverse (40403512), we get a palindrome (61933916).

The spelling of 21530404 in words is "twenty-one million, five hundred thirty thousand, four hundred four".