640684997 has 8 divisors (see below), whose sum is σ = 678874560. Its totient is φ = 602942400.

The previous prime is 640684991. The next prime is 640685039. The reversal of 640684997 is 799486046.

It is a happy number.

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 640684997 - 2⁸ = 640684741 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640684991) 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, 108788 + ... + 114525.

It is an arithmetic number, because the mean of its divisors is an integer number (84859320).

Almost surely, 2^640684997 is an apocalyptic number.

It is an amenable number.

640684997 is a deficient number, since it is larger than the sum of its proper divisors (38189563).

640684997 is a wasteful number, since it uses less digits than its factorization.

640684997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 223483.

The product of its (nonzero) digits is 2612736, while the sum is 53.

The square root of 640684997 is about 25311.7561026492. The cubic root of 640684997 is about 862.0812208250.

The spelling of 640684997 in words is "six hundred forty million, six hundred eighty-four thousand, nine hundred ninety-seven".