640278 has 32 divisors (see below), whose sum is σ = 1451520. Its totient is φ = 209160.

The previous prime is 640267. The next prime is 640279. The reversal of 640278 is 872046.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640279) by changing a digit.

640278 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 15 ways as a sum of consecutive naturals, for example, 3751 + ... + 3917.

It is an arithmetic number, because the mean of its divisors is an integer number (45360).

2⁶⁴⁰²⁷⁸ is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 640278, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (725760).

640278 is an abundant number, since it is smaller than the sum of its proper divisors (811242).

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

640278 is a wasteful number, since it uses less digits than its factorization.

640278 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 249 (or 243 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 640278 is about 800.1737311359. The cubic root of 640278 is about 86.1898635626.

The spelling of 640278 in words is "six hundred forty thousand, two hundred seventy-eight".