640664971 has 8 divisors (see below), whose sum is σ = 676392080. Its totient is φ = 605138688.

The previous prime is 640664963. The next prime is 640664993. The reversal of 640664971 is 179466046.

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

It is a cyclic number.

It is not a de Polignac number, because 640664971 - 2³ = 640664963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640664911) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 43626 + ... + 56431.

It is an arithmetic number, because the mean of its divisors is an integer number (84549010).

Almost surely, 2^640664971 is an apocalyptic number.

640664971 is a deficient number, since it is larger than the sum of its proper divisors (35727109).

640664971 is a wasteful number, since it uses less digits than its factorization.

640664971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100413.

The product of its (nonzero) digits is 217728, while the sum is 43.

The square root of 640664971 is about 25311.3605126236. The cubic root of 640664971 is about 862.0722386583.

The spelling of 640664971 in words is "six hundred forty million, six hundred sixty-four thousand, nine hundred seventy-one".