6640411681 has 2 divisors, whose sum is σ = 6640411682. Its totient is φ = 6640411680.

The previous prime is 6640411601. The next prime is 6640411691. The reversal of 6640411681 is 1861140466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6579805456 + 60606225 = 81116^2 + 7785^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-6640411681 is a prime.

It is a super-2 number, since 2×6640411681² = 88190134586322491522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 6640411681.

It is not a weakly prime, because it can be changed into another prime (6640411601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3320205840 + 3320205841.

It is an arithmetic number, because the mean of its divisors is an integer number (3320205841).

Almost surely, 2^6640411681 is an apocalyptic number.

It is an amenable number.

6640411681 is a deficient number, since it is larger than the sum of its proper divisors (1).

6640411681 is an equidigital number, since it uses as much as digits as its factorization.

6640411681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 27648, while the sum is 37.

The square root of 6640411681 is about 81488.7211888860. The cubic root of 6640411681 is about 1879.5981185072.

The spelling of 6640411681 in words is "six billion, six hundred forty million, four hundred eleven thousand, six hundred eighty-one".