640863 has 12 divisors (see below), whose sum is σ = 955968. Its totient is φ = 413280.

The previous prime is 640859. The next prime is 640873. The reversal of 640863 is 368046.

It is not a de Polignac number, because 640863 - 2² = 640859 is a prime.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

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

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 870 + ... + 1427.

It is an arithmetic number, because the mean of its divisors is an integer number (79664).

2⁶⁴⁰⁸⁶³ is an apocalyptic number.

640863 is a deficient number, since it is larger than the sum of its proper divisors (315105).

640863 is a wasteful number, since it uses less digits than its factorization.

640863 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2334 (or 2331 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 640863 is about 800.5391932941. The cubic root of 640863 is about 86.2161051441.

The spelling of 640863 in words is "six hundred forty thousand, eight hundred sixty-three".