21818404 has 24 divisors (see below), whose sum is σ = 39340728. Its totient is φ = 10583040.

The previous prime is 21818399. The next prime is 21818417. The reversal of 21818404 is 40481812.

It can be written as a sum of positive squares in 4 ways, for example, as 6200100 + 15618304 = 2490^2 + 3952^2 .

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 7 ways as a sum of consecutive naturals, for example, 20034 + ... + 21094.

It is an arithmetic number, because the mean of its divisors is an integer number (1639197).

Almost surely, 2^21818404 is an apocalyptic number.

It is an amenable number.

21818404 is a deficient number, since it is larger than the sum of its proper divisors (17522324).

21818404 is a wasteful number, since it uses less digits than its factorization.

21818404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1215 (or 1213 counting only the distinct ones).

The product of its (nonzero) digits is 2048, while the sum is 28.

The square root of 21818404 is about 4671.0174480513. The cubic root of 21818404 is about 279.4308336142.

It can be divided in two parts, 21818 and 404, that added together give a palindrome (22222).

The spelling of 21818404 in words is "twenty-one million, eight hundred eighteen thousand, four hundred four".