640657478 has 8 divisors (see below), whose sum is σ = 1017514872. Its totient is φ = 301485856.

The previous prime is 640657463. The next prime is 640657489. The reversal of 640657478 is 874756046.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9421400 + ... + 9421467.

It is an arithmetic number, because the mean of its divisors is an integer number (127189359).

Almost surely, 2^640657478 is an apocalyptic number.

640657478 is a deficient number, since it is larger than the sum of its proper divisors (376857394).

640657478 is a wasteful number, since it uses less digits than its factorization.

640657478 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18842886.

The product of its (nonzero) digits is 1128960, while the sum is 47.

The square root of 640657478 is about 25311.2124956510. The cubic root of 640657478 is about 862.0688778104.

The spelling of 640657478 in words is "six hundred forty million, six hundred fifty-seven thousand, four hundred seventy-eight".