640220651 has 8 divisors (see below), whose sum is σ = 732086784. Its totient is φ = 548456040.

The previous prime is 640220627. The next prime is 640220653. The reversal of 640220651 is 156022046.

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-640220651 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 640220651.

It is not an unprimeable number, because it can be changed into a prime (640220653) 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, 11345 + ... + 37538.

It is an arithmetic number, because the mean of its divisors is an integer number (91510848).

Almost surely, 2^640220651 is an apocalyptic number.

640220651 is a deficient number, since it is larger than the sum of its proper divisors (91866133).

640220651 is a wasteful number, since it uses less digits than its factorization.

640220651 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50761.

The product of its (nonzero) digits is 2880, while the sum is 26.

The square root of 640220651 is about 25302.5819038295. The cubic root of 640220651 is about 861.8729017518.

Adding to 640220651 its reverse (156022046), we get a palindrome (796242697).

The spelling of 640220651 in words is "six hundred forty million, two hundred twenty thousand, six hundred fifty-one".