640818 has 16 divisors (see below), whose sum is σ = 1424160. Its totient is φ = 213588.

The previous prime is 640793. The next prime is 640837. The reversal of 640818 is 818046.

640818 is a `hidden beast` number, since 640 + 8 + 18 = 666.

640818 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 640791 and 640800.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5880 + ... + 5987.

It is an arithmetic number, because the mean of its divisors is an integer number (89010).

2⁶⁴⁰⁸¹⁸ is an apocalyptic number.

640818 is an abundant number, since it is smaller than the sum of its proper divisors (783342).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640818 is a wasteful number, since it uses less digits than its factorization.

640818 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11878 (or 11872 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 640818 is about 800.5110867440. The cubic root of 640818 is about 86.2140871280.

The spelling of 640818 in words is "six hundred forty thousand, eight hundred eighteen".