21604371 has 4 divisors (see below), whose sum is σ = 28805832. Its totient is φ = 14402912.

The previous prime is 21604369. The next prime is 21604379. The reversal of 21604371 is 17340612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21604371 - 2¹ = 21604369 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21604379) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3600726 + ... + 3600731.

It is an arithmetic number, because the mean of its divisors is an integer number (7201458).

Almost surely, 2^21604371 is an apocalyptic number.

21604371 is a deficient number, since it is larger than the sum of its proper divisors (7201461).

21604371 is an equidigital number, since it uses as much as digits as its factorization.

21604371 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7201460.

The product of its (nonzero) digits is 1008, while the sum is 24.

The square root of 21604371 is about 4648.0502363894. The cubic root of 21604371 is about 278.5141142912.

Adding to 21604371 its reverse (17340612), we get a palindrome (38944983).

The spelling of 21604371 in words is "twenty-one million, six hundred four thousand, three hundred seventy-one".