640917 has 24 divisors (see below), whose sum is σ = 1010880. Its totient is φ = 389760.

The previous prime is 640907. The next prime is 640919. The reversal of 640917 is 719046.

640917 is a `hidden beast` number, since 640 + 9 + 17 = 666.

It is not a de Polignac number, because 640917 - 2⁴ = 640901 is a prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 640917.

It is not an unprimeable number, because it can be changed into a prime (640919) by changing a digit.

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 23 ways as a sum of consecutive naturals, for example, 8992 + ... + 9062.

It is an arithmetic number, because the mean of its divisors is an integer number (42120).

2⁶⁴⁰⁹¹⁷ is an apocalyptic number.

It is an amenable number.

640917 is a deficient number, since it is larger than the sum of its proper divisors (369963).

640917 is a wasteful number, since it uses less digits than its factorization.

640917 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 153 (or 150 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 27.

The square root of 640917 is about 800.5729198518. The cubic root of 640917 is about 86.2185266387.

The spelling of 640917 in words is "six hundred forty thousand, nine hundred seventeen".