640440035665 has 4 divisors (see below), whose sum is σ = 768528042804. Its totient is φ = 512352028528.

The previous prime is 640440035663. The next prime is 640440035693. The reversal of 640440035665 is 566530044046.

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 140438312001 + 500001723664 = 374751^2 + 707108^2 .

It is a cyclic number.

It is not a de Polignac number, because 640440035665 - 2¹ = 640440035663 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640440035663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64044003562 + ... + 64044003571.

It is an arithmetic number, because the mean of its divisors is an integer number (192132010701).

Almost surely, 2^640440035665 is an apocalyptic number.

It is an amenable number.

640440035665 is a deficient number, since it is larger than the sum of its proper divisors (128088007139).

640440035665 is a wasteful number, since it uses less digits than its factorization.

640440035665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128088007138.

The product of its (nonzero) digits is 1036800, while the sum is 43.

The spelling of 640440035665 in words is "six hundred forty billion, four hundred forty million, thirty-five thousand, six hundred sixty-five".