21004436 has 12 divisors (see below), whose sum is σ = 37261812. Its totient is φ = 10358208.

The previous prime is 21004387. The next prime is 21004447. The reversal of 21004436 is 63440012.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 4243600 + 16760836 = 2060^2 + 4094^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 35675 + ... + 36258.

It is an arithmetic number, because the mean of its divisors is an integer number (3105151).

Almost surely, 2^21004436 is an apocalyptic number.

It is an amenable number.

21004436 is a deficient number, since it is larger than the sum of its proper divisors (16257376).

21004436 is a wasteful number, since it uses less digits than its factorization.

21004436 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72010 (or 72008 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 20.

The square root of 21004436 is about 4583.0596766789. The cubic root of 21004436 is about 275.9118426000.

Adding to 21004436 its reverse (63440012), we get a palindrome (84444448).

The spelling of 21004436 in words is "twenty-one million, four thousand, four hundred thirty-six".