639621949 has 2 divisors, whose sum is σ = 639621950. Its totient is φ = 639621948.

The previous prime is 639621937. The next prime is 639622007. The reversal of 639621949 is 949126936.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 557809924 + 81812025 = 23618^2 + 9045^2 .

It is a cyclic number.

It is not a de Polignac number, because 639621949 - 2¹³ = 639613757 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639621929) 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, 319810974 + 319810975.

It is an arithmetic number, because the mean of its divisors is an integer number (319810975).

Almost surely, 2^639621949 is an apocalyptic number.

It is an amenable number.

639621949 is a deficient number, since it is larger than the sum of its proper divisors (1).

639621949 is an equidigital number, since it uses as much as digits as its factorization.

639621949 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 629856, while the sum is 49.

The square root of 639621949 is about 25290.7482886529. The cubic root of 639621949 is about 861.6041579679.

The spelling of 639621949 in words is "six hundred thirty-nine million, six hundred twenty-one thousand, nine hundred forty-nine".