641605985 has 4 divisors (see below), whose sum is σ = 769927188. Its totient is φ = 513284784.

The previous prime is 641605981. The next prime is 641606033. The reversal of 641605985 is 589506146.

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 482417296 + 159188689 = 21964^2 + 12617^2 .

It is a cyclic number.

It is not a de Polignac number, because 641605985 - 2² = 641605981 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (641605981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64160594 + ... + 64160603.

It is an arithmetic number, because the mean of its divisors is an integer number (192481797).

Almost surely, 2^641605985 is an apocalyptic number.

It is an amenable number.

641605985 is a deficient number, since it is larger than the sum of its proper divisors (128321203).

641605985 is a wasteful number, since it uses less digits than its factorization.

641605985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 128321202.

The product of its (nonzero) digits is 259200, while the sum is 44.

The square root of 641605985 is about 25329.9424594688. The cubic root of 641605985 is about 862.4941051197.

The spelling of 641605985 in words is "six hundred forty-one million, six hundred five thousand, nine hundred eighty-five".