21604037 has 16 divisors (see below), whose sum is σ = 26745600. Its totient is φ = 16993152.

The previous prime is 21604031. The next prime is 21604057. The reversal of 21604037 is 73040612.

It is a cyclic number.

It is not a de Polignac number, because 21604037 - 2⁴ = 21604021 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21604031) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17513 + ... + 18705.

It is an arithmetic number, because the mean of its divisors is an integer number (1671600).

Almost surely, 2^21604037 is an apocalyptic number.

It is an amenable number.

21604037 is a deficient number, since it is larger than the sum of its proper divisors (5141563).

21604037 is a wasteful number, since it uses less digits than its factorization.

21604037 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1412.

The product of its (nonzero) digits is 1008, while the sum is 23.

The square root of 21604037 is about 4648.0143072069. The cubic root of 21604037 is about 278.5126790231.

Adding to 21604037 its reverse (73040612), we get a palindrome (94644649).

The spelling of 21604037 in words is "twenty-one million, six hundred four thousand, thirty-seven".