639649265891 has 2 divisors, whose sum is σ = 639649265892. Its totient is φ = 639649265890.

The previous prime is 639649265839. The next prime is 639649265917. The reversal of 639649265891 is 198562946936.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-639649265891 is a prime.

It is not a weakly prime, because it can be changed into another prime (639649265491) 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, 319824632945 + 319824632946.

It is an arithmetic number, because the mean of its divisors is an integer number (319824632946).

Almost surely, 2^639649265891 is an apocalyptic number.

639649265891 is a deficient number, since it is larger than the sum of its proper divisors (1).

639649265891 is an equidigital number, since it uses as much as digits as its factorization.

639649265891 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 151165440, while the sum is 68.

The spelling of 639649265891 in words is "six hundred thirty-nine billion, six hundred forty-nine million, two hundred sixty-five thousand, eight hundred ninety-one".