666849229621 has 2 divisors, whose sum is σ = 666849229622. Its totient is φ = 666849229620.

The previous prime is 666849229619. The next prime is 666849229639. The reversal of 666849229621 is 126922948666.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 456800256900 + 210048972721 = 675870^2 + 458311^2 .

It is a cyclic number.

It is not a de Polignac number, because 666849229621 - 2¹ = 666849229619 is a prime.

It is a super-2 number, since 2×666849229621² (a number of 24 digits) contains 22 as substring.

Together with 666849229619, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 666849229621.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (666849229691) 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, 333424614810 + 333424614811.

It is an arithmetic number, because the mean of its divisors is an integer number (333424614811).

Almost surely, 2^666849229621 is an apocalyptic number.

It is an amenable number.

666849229621 is a deficient number, since it is larger than the sum of its proper divisors (1).

666849229621 is an equidigital number, since it uses as much as digits as its factorization.

666849229621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 26873856, while the sum is 61.

The spelling of 666849229621 in words is "six hundred sixty-six billion, eight hundred forty-nine million, two hundred twenty-nine thousand, six hundred twenty-one".