21602605 has 4 divisors (see below), whose sum is σ = 25923132. Its totient is φ = 17282080.

The previous prime is 21602591. The next prime is 21602611. The reversal of 21602605 is 50620612.

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

It can be written as a sum of positive squares in 2 ways, for example, as 3378244 + 18224361 = 1838^2 + 4269^2 .

It is not a de Polignac number, because 21602605 - 2¹⁷ = 21471533 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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, 2160256 + ... + 2160265.

It is an arithmetic number, because the mean of its divisors is an integer number (6480783).

Almost surely, 2^21602605 is an apocalyptic number.

It is an amenable number.

21602605 is a deficient number, since it is larger than the sum of its proper divisors (4320527).

21602605 is an equidigital number, since it uses as much as digits as its factorization.

21602605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4320526.

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

The square root of 21602605 is about 4647.8602603779. The cubic root of 21602605 is about 278.5065252509.

The spelling of 21602605 in words is "twenty-one million, six hundred two thousand, six hundred five".