20642665 has 4 divisors (see below), whose sum is σ = 24771204. Its totient is φ = 16514128.

The previous prime is 20642659. The next prime is 20642689. The reversal of 20642665 is 56624602.

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 3111696 + 17530969 = 1764^2 + 4187^2 .

It is a cyclic number.

It is not a de Polignac number, because 20642665 - 2¹¹ = 20640617 is a prime.

It is a super-2 number, since 2×20642665² = 852239236604450, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) 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 an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2064262 + ... + 2064271.

It is an arithmetic number, because the mean of its divisors is an integer number (6192801).

Almost surely, 2^20642665 is an apocalyptic number.

It is an amenable number.

20642665 is a deficient number, since it is larger than the sum of its proper divisors (4128539).

20642665 is an equidigital number, since it uses as much as digits as its factorization.

20642665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4128538.

The product of its (nonzero) digits is 17280, while the sum is 31.

The square root of 20642665 is about 4543.4199673814. The cubic root of 20642665 is about 274.3185995081.

The spelling of 20642665 in words is "twenty million, six hundred forty-two thousand, six hundred sixty-five".