21604367 has 4 divisors (see below), whose sum is σ = 21877920. Its totient is φ = 21330816.

The previous prime is 21604339. The next prime is 21604369. The reversal of 21604367 is 76340612.

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 21604367 - 2¹⁰ = 21603343 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 (21604369) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 136658 + ... + 136815.

It is an arithmetic number, because the mean of its divisors is an integer number (5469480).

Almost surely, 2^21604367 is an apocalyptic number.

21604367 is a deficient number, since it is larger than the sum of its proper divisors (273553).

21604367 is an equidigital number, since it uses as much as digits as its factorization.

21604367 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 273552.

The product of its (nonzero) digits is 6048, while the sum is 29.

The square root of 21604367 is about 4648.0498061015. The cubic root of 21604367 is about 278.5140971025.

Adding to 21604367 its reverse (76340612), we get a palindrome (97944979).

The spelling of 21604367 in words is "twenty-one million, six hundred four thousand, three hundred sixty-seven".