640250855861 has 2 divisors, whose sum is σ = 640250855862. Its totient is φ = 640250855860.

The previous prime is 640250855791. The next prime is 640250855869. The reversal of 640250855861 is 168558052046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 604000980625 + 36249875236 = 777175^2 + 190394^2 .

It is a cyclic number.

It is not a de Polignac number, because 640250855861 - 2¹⁴ = 640250839477 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640250855869) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320125427930 + 320125427931.

It is an arithmetic number, because the mean of its divisors is an integer number (320125427931).

Almost surely, 2^640250855861 is an apocalyptic number.

It is an amenable number.

640250855861 is a deficient number, since it is larger than the sum of its proper divisors (1).

640250855861 is an equidigital number, since it uses as much as digits as its factorization.

640250855861 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2304000, while the sum is 50.

The spelling of 640250855861 in words is "six hundred forty billion, two hundred fifty million, eight hundred fifty-five thousand, eight hundred sixty-one".