640522991 has 8 divisors (see below), whose sum is σ = 678716784. Its totient is φ = 602386560.

The previous prime is 640522973. The next prime is 640522999. The reversal of 640522991 is 199225046.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640522991 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 (640522999) 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, 9836 + ... + 37118.

It is an arithmetic number, because the mean of its divisors is an integer number (84839598).

Almost surely, 2^640522991 is an apocalyptic number.

640522991 is a deficient number, since it is larger than the sum of its proper divisors (38193793).

640522991 is a wasteful number, since it uses less digits than its factorization.

640522991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28681.

The product of its (nonzero) digits is 38880, while the sum is 38.

The square root of 640522991 is about 25308.5556877511. Note that the first 3 decimals coincide. The cubic root of 640522991 is about 862.0085516743.

The spelling of 640522991 in words is "six hundred forty million, five hundred twenty-two thousand, nine hundred ninety-one".