640308478 has 4 divisors (see below), whose sum is σ = 960462720. Its totient is φ = 320154238.

The previous prime is 640308467. The next prime is 640308497. The reversal of 640308478 is 874803046.

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

It is a self number, because there is not a number n which added to its sum of digits gives 640308478.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 160077118 + ... + 160077121.

It is an arithmetic number, because the mean of its divisors is an integer number (240115680).

Almost surely, 2^640308478 is an apocalyptic number.

640308478 is a deficient number, since it is larger than the sum of its proper divisors (320154242).

640308478 is a wasteful number, since it uses less digits than its factorization.

640308478 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 320154241.

The product of its (nonzero) digits is 129024, while the sum is 40.

The square root of 640308478 is about 25304.3173786609. The cubic root of 640308478 is about 861.9123112118.

The spelling of 640308478 in words is "six hundred forty million, three hundred eight thousand, four hundred seventy-eight".