21540404 has 12 divisors (see below), whose sum is σ = 37765728. Its totient is φ = 10750200.

The previous prime is 21540383. The next prime is 21540437. The reversal of 21540404 is 40404512.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2432 + ... + 6999.

It is an arithmetic number, because the mean of its divisors is an integer number (3147144).

Almost surely, 2^21540404 is an apocalyptic number.

It is an amenable number.

21540404 is a deficient number, since it is larger than the sum of its proper divisors (16225324).

21540404 is a wasteful number, since it uses less digits than its factorization.

21540404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10006 (or 10004 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 20.

The square root of 21540404 is about 4641.1640781166. The cubic root of 21540404 is about 278.2389643464.

Adding to 21540404 its reverse (40404512), we get a palindrome (61944916).

The spelling of 21540404 in words is "twenty-one million, five hundred forty thousand, four hundred four".