640811747 has 2 divisors, whose sum is σ = 640811748. Its totient is φ = 640811746.

The previous prime is 640811741. The next prime is 640811807. The reversal of 640811747 is 747118046.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 640811747 - 2⁶ = 640811683 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 640811747.

It is not a weakly prime, because it can be changed into another prime (640811741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320405873 + 320405874.

It is an arithmetic number, because the mean of its divisors is an integer number (320405874).

Almost surely, 2^640811747 is an apocalyptic number.

640811747 is a deficient number, since it is larger than the sum of its proper divisors (1).

640811747 is an equidigital number, since it uses as much as digits as its factorization.

640811747 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 37632, while the sum is 38.

The square root of 640811747 is about 25314.2597561137. The cubic root of 640811747 is about 862.1380670601.

The spelling of 640811747 in words is "six hundred forty million, eight hundred eleven thousand, seven hundred forty-seven".