640918 has 8 divisors (see below), whose sum is σ = 1003248. Its totient is φ = 306504.

The previous prime is 640907. The next prime is 640919. The reversal of 640918 is 819046.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

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 3 ways as a sum of consecutive naturals, for example, 6921 + ... + 7012.

It is an arithmetic number, because the mean of its divisors is an integer number (125406).

2⁶⁴⁰⁹¹⁸ is an apocalyptic number.

640918 is a deficient number, since it is larger than the sum of its proper divisors (362330).

640918 is a wasteful number, since it uses less digits than its factorization.

640918 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13958.

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 640918 is about 800.5735444043. The cubic root of 640918 is about 86.2185714800.

The spelling of 640918 in words is "six hundred forty thousand, nine hundred eighteen".