645581665 has 8 divisors (see below), whose sum is σ = 799688448. Its totient is φ = 499805040.

The previous prime is 645581659. The next prime is 645581669. The reversal of 645581665 is 566185546.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 645581665 - 2⁵ = 645581633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645581669) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2082367 + ... + 2082676.

It is an arithmetic number, because the mean of its divisors is an integer number (99961056).

Almost surely, 2^645581665 is an apocalyptic number.

It is an amenable number.

645581665 is a deficient number, since it is larger than the sum of its proper divisors (154106783).

645581665 is a wasteful number, since it uses less digits than its factorization.

645581665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4165079.

The product of its digits is 864000, while the sum is 46.

The square root of 645581665 is about 25408.2991363058. The cubic root of 645581665 is about 864.2719056081.

The spelling of 645581665 in words is "six hundred forty-five million, five hundred eighty-one thousand, six hundred sixty-five".