21090404 has 24 divisors (see below), whose sum is σ = 39916800. Its totient is φ = 9712256.

The previous prime is 21090401. The next prime is 21090409. The reversal of 21090404 is 40409012.

21090404 = 23² + 24² + ... + 398².

It is not an unprimeable number, because it can be changed into a prime (21090401) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 104 + ... + 6495.

It is an arithmetic number, because the mean of its divisors is an integer number (1663200).

Almost surely, 2^21090404 is an apocalyptic number.

It is an amenable number.

21090404 is a deficient number, since it is larger than the sum of its proper divisors (18826396).

21090404 is a wasteful number, since it uses less digits than its factorization.

21090404 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6667 (or 6665 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 21090404 is about 4592.4289869306. The cubic root of 21090404 is about 276.2877521210.

Adding to 21090404 its reverse (40409012), we get a palindrome (61499416).

The spelling of 21090404 in words is "twenty-one million, ninety thousand, four hundred four".