640878 has 16 divisors (see below), whose sum is σ = 1464960. Its totient is φ = 183096.

The previous prime is 640873. The next prime is 640891. The reversal of 640878 is 878046.

It is a super-2 number, since 2×640878² = 821449221768, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640873) by changing a digit.

640878 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7588 + ... + 7671.

It is an arithmetic number, because the mean of its divisors is an integer number (91560).

2⁶⁴⁰⁸⁷⁸ is an apocalyptic number.

640878 is an abundant number, since it is smaller than the sum of its proper divisors (824082).

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

640878 is a wasteful number, since it uses less digits than its factorization.

640878 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15271.

The product of its (nonzero) digits is 10752, while the sum is 33.

The square root of 640878 is about 800.5485619249. The cubic root of 640878 is about 86.2167777952.

The spelling of 640878 in words is "six hundred forty thousand, eight hundred seventy-eight".