639744174538649 has 2 divisors, whose sum is σ = 639744174538650. Its totient is φ = 639744174538648.

The previous prime is 639744174538633. The next prime is 639744174538741. The reversal of 639744174538649 is 946835471447936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 427869018150025 + 211875156388624 = 20684995^2 + 14555932^2 .

It is a cyclic number.

It is not a de Polignac number, because 639744174538649 - 2⁴ = 639744174538633 is a prime.

It is a super-2 number, since 2×639744174538649² (a number of 30 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (639744174538549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319872087269324 + 319872087269325.

It is an arithmetic number, because the mean of its divisors is an integer number (319872087269325).

Almost surely, 2^{639744174538649} is an apocalyptic number.

It is an amenable number.

639744174538649 is a deficient number, since it is larger than the sum of its proper divisors (1).

639744174538649 is an equidigital number, since it uses as much as digits as its factorization.

639744174538649 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13168189440, while the sum is 80.

The spelling of 639744174538649 in words is "six hundred thirty-nine trillion, seven hundred forty-four billion, one hundred seventy-four million, five hundred thirty-eight thousand, six hundred forty-nine".