21662605 has 4 divisors (see below), whose sum is σ = 25995132. Its totient is φ = 17330080.

The previous prime is 21662591. The next prime is 21662609. The reversal of 21662605 is 50626612.

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 15888196 + 5774409 = 3986^2 + 2403^2 .

It is not a de Polignac number, because 21662605 - 2⁷ = 21662477 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 (21662609) 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, 2166256 + ... + 2166265.

It is an arithmetic number, because the mean of its divisors is an integer number (6498783).

Almost surely, 2^21662605 is an apocalyptic number.

It is an amenable number.

21662605 is a deficient number, since it is larger than the sum of its proper divisors (4332527).

21662605 is an equidigital number, since it uses as much as digits as its factorization.

21662605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4332526.

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21662605 is about 4654.3103678203. The cubic root of 21662605 is about 278.7641322173.

The spelling of 21662605 in words is "twenty-one million, six hundred sixty-two thousand, six hundred five".