640016991 has 8 divisors (see below), whose sum is σ = 948173360. Its totient is φ = 426677976.

The previous prime is 640016987. The next prime is 640017013. The reversal of 640016991 is 199610046.

640016991 is a `hidden beast` number, since 6 + 400 + 169 + 91 = 666.

It is not a de Polignac number, because 640016991 - 2² = 640016987 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640016891) 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, 11852140 + ... + 11852193.

It is an arithmetic number, because the mean of its divisors is an integer number (118521670).

Almost surely, 2^640016991 is an apocalyptic number.

640016991 is a deficient number, since it is larger than the sum of its proper divisors (308156369).

640016991 is a wasteful number, since it uses less digits than its factorization.

640016991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23704342 (or 23704336 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 36.

The square root of 640016991 is about 25298.5570932415. The cubic root of 640016991 is about 861.7815021952.

The spelling of 640016991 in words is "six hundred forty million, sixteen thousand, nine hundred ninety-one".