640855 has 8 divisors (see below), whose sum is σ = 780912. Its totient is φ = 504768.

The previous prime is 640853. The next prime is 640859. The reversal of 640855 is 558046.

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

It is a cyclic number.

It is not a de Polignac number, because 640855 - 2¹ = 640853 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640853) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 622 + ... + 1291.

It is an arithmetic number, because the mean of its divisors is an integer number (97614).

2⁶⁴⁰⁸⁵⁵ is an apocalyptic number.

640855 is a deficient number, since it is larger than the sum of its proper divisors (140057).

640855 is a wasteful number, since it uses less digits than its factorization.

640855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1985.

The product of its (nonzero) digits is 4800, while the sum is 28.

The square root of 640855 is about 800.5341966462. The cubic root of 640855 is about 86.2157463926.

The spelling of 640855 in words is "six hundred forty thousand, eight hundred fifty-five".