7666821881 has 2 divisors, whose sum is σ = 7666821882. Its totient is φ = 7666821880.

The previous prime is 7666821829. The next prime is 7666821889. The reversal of 7666821881 is 1881286667.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6089461225 + 1577360656 = 78035^2 + 39716^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-7666821881 is a prime.

It is a super-2 number, since 2×7666821881² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (7666821889) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3833410940 + 3833410941.

It is an arithmetic number, because the mean of its divisors is an integer number (3833410941).

Almost surely, 2^7666821881 is an apocalyptic number.

It is an amenable number.

7666821881 is a deficient number, since it is larger than the sum of its proper divisors (1).

7666821881 is an equidigital number, since it uses as much as digits as its factorization.

7666821881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1548288, while the sum is 53.

The square root of 7666821881 is about 87560.3899089080. The cubic root of 7666821881 is about 1971.8405399198.

The spelling of 7666821881 in words is "seven billion, six hundred sixty-six million, eight hundred twenty-one thousand, eight hundred eighty-one".