21604135 has 16 divisors (see below), whose sum is σ = 29753856. Its totient is φ = 14751648.

The previous prime is 21604109. The next prime is 21604139. The reversal of 21604135 is 53140612.

It is a cyclic number.

It is not a de Polignac number, because 21604135 - 2¹⁵ = 21571367 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21604139) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8032 + ... + 10378.

It is an arithmetic number, because the mean of its divisors is an integer number (1859616).

Almost surely, 2^21604135 is an apocalyptic number.

21604135 is a deficient number, since it is larger than the sum of its proper divisors (8149721).

21604135 is a wasteful number, since it uses less digits than its factorization.

21604135 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2622.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21604135 is about 4648.0248493312. The cubic root of 21604135 is about 278.5131001512.

Adding to 21604135 its reverse (53140612), we get a palindrome (74744747).

The spelling of 21604135 in words is "twenty-one million, six hundred four thousand, one hundred thirty-five".