640899 has 16 divisors (see below), whose sum is σ = 1085440. Its totient is φ = 366120.

The previous prime is 640891. The next prime is 640901. The reversal of 640899 is 998046.

640899 is a `hidden beast` number, since 640 + 8 + 9 + 9 = 666.

640899 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 640899 - 2³ = 640891 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640891) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1507 + ... + 1884.

It is an arithmetic number, because the mean of its divisors is an integer number (67840).

2⁶⁴⁰⁸⁹⁹ is an apocalyptic number.

640899 is a deficient number, since it is larger than the sum of its proper divisors (444541).

640899 is a wasteful number, since it uses less digits than its factorization.

640899 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3407 (or 3401 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The square root of 640899 is about 800.5616778238. The cubic root of 640899 is about 86.2177194890.

The spelling of 640899 in words is "six hundred forty thousand, eight hundred ninety-nine".