641909665 has 4 divisors (see below), whose sum is σ = 770291604. Its totient is φ = 513527728.

The previous prime is 641909663. The next prime is 641909669. The reversal of 641909665 is 566909146.

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 469328896 + 172580769 = 21664^2 + 13137^2 .

It is a cyclic number.

It is not a de Polignac number, because 641909665 - 2¹ = 641909663 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (641909663) 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, 64190962 + ... + 64190971.

It is an arithmetic number, because the mean of its divisors is an integer number (192572901).

Almost surely, 2^641909665 is an apocalyptic number.

It is an amenable number.

641909665 is a deficient number, since it is larger than the sum of its proper divisors (128381939).

641909665 is a wasteful number, since it uses less digits than its factorization.

641909665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128381938.

The product of its (nonzero) digits is 349920, while the sum is 46.

The square root of 641909665 is about 25335.9362368948. The cubic root of 641909665 is about 862.6301600107.

The spelling of 641909665 in words is "six hundred forty-one million, nine hundred nine thousand, six hundred sixty-five".