640668828651 has 16 divisors (see below), whose sum is σ = 858754068480. Its totient is φ = 424848366080.

The previous prime is 640668828539. The next prime is 640668828661. The reversal of 640668828651 is 156828866046.

It is a cyclic number.

It is not a de Polignac number, because 640668828651 - 2⁷ = 640668828523 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640668828661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12226315 + ... + 12278603.

It is an arithmetic number, because the mean of its divisors is an integer number (53672129280).

Almost surely, 2^640668828651 is an apocalyptic number.

640668828651 is a deficient number, since it is larger than the sum of its proper divisors (218085239829).

640668828651 is a wasteful number, since it uses less digits than its factorization.

640668828651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 73866.

The product of its (nonzero) digits is 26542080, while the sum is 60.

The spelling of 640668828651 in words is "six hundred forty billion, six hundred sixty-eight million, eight hundred twenty-eight thousand, six hundred fifty-one".