640161665 has 32 divisors (see below), whose sum is σ = 904780800. Its totient is φ = 428670720.

The previous prime is 640161649. The next prime is 640161671. The reversal of 640161665 is 566161046.

It is not a de Polignac number, because 640161665 - 2⁴ = 640161649 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 363056 + ... + 364814.

It is an arithmetic number, because the mean of its divisors is an integer number (28274400).

Almost surely, 2^640161665 is an apocalyptic number.

640161665 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

640161665 is a deficient number, since it is larger than the sum of its proper divisors (264619135).

640161665 is a wasteful number, since it uses less digits than its factorization.

640161665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2297.

The product of its (nonzero) digits is 25920, while the sum is 35.

The square root of 640161665 is about 25301.4162647074. The cubic root of 640161665 is about 861.8464317131.

The spelling of 640161665 in words is "six hundred forty million, one hundred sixty-one thousand, six hundred sixty-five".