16640665 has 4 divisors (see below), whose sum is σ = 19968804. Its totient is φ = 13312528.

The previous prime is 16640651. The next prime is 16640681. The reversal of 16640665 is 56604661.

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 2585664 + 14055001 = 1608^2 + 3749^2 .

It is a cyclic number.

It is not a de Polignac number, because 16640665 - 2¹⁵ = 16607897 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 16640665.

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, 1664062 + ... + 1664071.

It is an arithmetic number, because the mean of its divisors is an integer number (4992201).

Almost surely, 2^16640665 is an apocalyptic number.

It is an amenable number.

16640665 is a deficient number, since it is larger than the sum of its proper divisors (3328139).

16640665 is an equidigital number, since it uses as much as digits as its factorization.

16640665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3328138.

The product of its (nonzero) digits is 25920, while the sum is 34.

The square root of 16640665 is about 4079.2971208285. The cubic root of 16640665 is about 255.3035728429.

The spelling of 16640665 in words is "sixteen million, six hundred forty thousand, six hundred sixty-five".