669906661 has 2 divisors, whose sum is σ = 669906662. Its totient is φ = 669906660.

The previous prime is 669906659. The next prime is 669906707. The reversal of 669906661 is 166609966.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 668481025 + 1425636 = 25855^2 + 1194^2 .

It is a cyclic number.

It is not a de Polignac number, because 669906661 - 2¹ = 669906659 is a prime.

Together with 669906659, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (669906631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334953330 + 334953331.

It is an arithmetic number, because the mean of its divisors is an integer number (334953331).

Almost surely, 2^669906661 is an apocalyptic number.

It is an amenable number.

669906661 is a deficient number, since it is larger than the sum of its proper divisors (1).

669906661 is an equidigital number, since it uses as much as digits as its factorization.

669906661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 629856, while the sum is 49.

The square root of 669906661 is about 25882.5551482075. Note that the first 3 decimals coincide. The cubic root of 669906661 is about 874.9933761675.

The spelling of 669906661 in words is "six hundred sixty-nine million, nine hundred six thousand, six hundred sixty-one".