21008404 has 24 divisors (see below), whose sum is σ = 37485000. Its totient is φ = 10300800.

The previous prime is 21008401. The next prime is 21008419. The reversal of 21008404 is 40480012.

It can be written as a sum of positive squares in 4 ways, for example, as 6492304 + 14516100 = 2548^2 + 3810^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21008401) 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, 60022 + ... + 60370.

It is an arithmetic number, because the mean of its divisors is an integer number (1561875).

Almost surely, 2^21008404 is an apocalyptic number.

It is an amenable number.

21008404 is a deficient number, since it is larger than the sum of its proper divisors (16476596).

21008404 is a wasteful number, since it uses less digits than its factorization.

21008404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 603 (or 601 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 19.

The square root of 21008404 is about 4583.4925548101. The cubic root of 21008404 is about 275.9292159024.

Adding to 21008404 its reverse (40480012), we get a palindrome (61488416).

It can be divided in two parts, 21008 and 404, that added together give a palindrome (21412).

The spelling of 21008404 in words is "twenty-one million, eight thousand, four hundred four".