640078 has 4 divisors (see below), whose sum is σ = 960120. Its totient is φ = 320038.

The previous prime is 640069. The next prime is 640099. The reversal of 640078 is 870046.

It is a semiprime because it is the product of two primes.

It is an Ulam number.

It is a congruent number.

It is an unprimeable number.

640078 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 as a sum of consecutive naturals, namely, 160018 + ... + 160021.

It is an arithmetic number, because the mean of its divisors is an integer number (240030).

2⁶⁴⁰⁰⁷⁸ is an apocalyptic number.

640078 is a deficient number, since it is larger than the sum of its proper divisors (320042).

640078 is a wasteful number, since it uses less digits than its factorization.

640078 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 320041.

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

The square root of 640078 is about 800.0487485147. The cubic root of 640078 is about 86.1808884154.

The spelling of 640078 in words is "six hundred forty thousand, seventy-eight".