78640 has 20 divisors (see below), whose sum is σ = 183024. Its totient is φ = 31424.

The previous prime is 78623. The next prime is 78643. The reversal of 78640 is 4687.

It is a tau number, because it is divible by the number of its divisors (20).

It is not an unprimeable number, because it can be changed into a prime (78643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 412 + ... + 571.

2⁷⁸⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

78640 is an abundant number, since it is smaller than the sum of its proper divisors (104384).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (91512).

78640 is a wasteful number, since it uses less digits than its factorization.

78640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 996 (or 990 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 78640 is about 280.4282439413. The cubic root of 78640 is about 42.8431276924.

The spelling of 78640 in words is "seventy-eight thousand, six hundred forty".