640686378 has 16 divisors (see below), whose sum is σ = 1356747840. Its totient is φ = 200999616.

The previous prime is 640686349. The next prime is 640686427. The reversal of 640686378 is 873686046.

It is a happy number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3140518 + ... + 3140721.

It is an arithmetic number, because the mean of its divisors is an integer number (84796740).

Almost surely, 2^640686378 is an apocalyptic number.

640686378 is an abundant number, since it is smaller than the sum of its proper divisors (716061462).

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

640686378 is a wasteful number, since it uses less digits than its factorization.

640686378 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6281261.

The product of its (nonzero) digits is 1161216, while the sum is 48.

The square root of 640686378 is about 25311.7833824486. The cubic root of 640686378 is about 862.0818402315.

The spelling of 640686378 in words is "six hundred forty million, six hundred eighty-six thousand, three hundred seventy-eight".