640209616649 has 2 divisors, whose sum is σ = 640209616650. Its totient is φ = 640209616648.

The previous prime is 640209616643. The next prime is 640209616661. The reversal of 640209616649 is 946616902046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 567676354249 + 72533262400 = 753443^2 + 269320^2 .

It is a cyclic number.

It is not a de Polignac number, because 640209616649 - 2²⁰ = 640208568073 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 640209616649.

It is not a weakly prime, because it can be changed into another prime (640209616643) 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, 320104808324 + 320104808325.

It is an arithmetic number, because the mean of its divisors is an integer number (320104808325).

Almost surely, 2^640209616649 is an apocalyptic number.

It is an amenable number.

640209616649 is a deficient number, since it is larger than the sum of its proper divisors (1).

640209616649 is an equidigital number, since it uses as much as digits as its factorization.

640209616649 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3359232, while the sum is 53.

The spelling of 640209616649 in words is "six hundred forty billion, two hundred nine million, six hundred sixteen thousand, six hundred forty-nine".