6640968857 has 2 divisors, whose sum is σ = 6640968858. Its totient is φ = 6640968856.

The previous prime is 6640968839. The next prime is 6640968881. The reversal of 6640968857 is 7588690466.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 3417454681 + 3223514176 = 58459^2 + 56776^2 .

It is a cyclic number.

It is not a de Polignac number, because 6640968857 - 2¹² = 6640964761 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 6640968796 and 6640968805.

It is not a weakly prime, because it can be changed into another prime (6640668857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3320484428 + 3320484429.

It is an arithmetic number, because the mean of its divisors is an integer number (3320484429).

Almost surely, 2^6640968857 is an apocalyptic number.

It is an amenable number.

6640968857 is a deficient number, since it is larger than the sum of its proper divisors (1).

6640968857 is an equidigital number, since it uses as much as digits as its factorization.

6640968857 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17418240, while the sum is 59.

The square root of 6640968857 is about 81492.1398479633. The cubic root of 6640968857 is about 1879.6506874202.

The spelling of 6640968857 in words is "six billion, six hundred forty million, nine hundred sixty-eight thousand, eight hundred fifty-seven".