6642939817 has 2 divisors, whose sum is σ = 6642939818. Its totient is φ = 6642939816.

The previous prime is 6642939773. The next prime is 6642939871. The reversal of 6642939817 is 7189392466.

Together with next prime (6642939871) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 6537692736 + 105247081 = 80856^2 + 10259^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6642939817 is a prime.

It is not a weakly prime, because it can be changed into another prime (6642939217) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3321469908 + 3321469909.

It is an arithmetic number, because the mean of its divisors is an integer number (3321469909).

Almost surely, 2^6642939817 is an apocalyptic number.

It is an amenable number.

6642939817 is a deficient number, since it is larger than the sum of its proper divisors (1).

6642939817 is an equidigital number, since it uses as much as digits as its factorization.

6642939817 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3919104, while the sum is 55.

The square root of 6642939817 is about 81504.2318962641. The cubic root of 6642939817 is about 1879.8366216292.

The spelling of 6642939817 in words is "six billion, six hundred forty-two million, nine hundred thirty-nine thousand, eight hundred seventeen".