21440404 has 6 divisors (see below), whose sum is σ = 37520714. Its totient is φ = 10720200.

The previous prime is 21440399. The next prime is 21440411. The reversal of 21440404 is 40404412.

It can be written as a sum of positive squares in only one way, i.e., 19184400 + 2256004 = 4380^2 + 1502^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2680047 + ... + 2680054.

Almost surely, 2^21440404 is an apocalyptic number.

It is an amenable number.

21440404 is a deficient number, since it is larger than the sum of its proper divisors (16080310).

21440404 is a wasteful number, since it uses less digits than its factorization.

21440404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5360105 (or 5360103 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 19.

The square root of 21440404 is about 4630.3783862661. The cubic root of 21440404 is about 277.8077272360.

Adding to 21440404 its reverse (40404412), we get a palindrome (61844816).

The spelling of 21440404 in words is "twenty-one million, four hundred forty thousand, four hundred four".