669661 has 2 divisors, whose sum is σ = 669662. Its totient is φ = 669660.

The previous prime is 669659. The next prime is 669667. The reversal of 669661 is 166966.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 632025 + 37636 = 795^2 + 194^2 .

It is a cyclic number.

It is not a de Polignac number, because 669661 - 2¹ = 669659 is a prime.

Together with 669659, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (669667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 334830 + 334831.

It is an arithmetic number, because the mean of its divisors is an integer number (334831).

2⁶⁶⁹⁶⁶¹ is an apocalyptic number.

It is an amenable number.

669661 is a deficient number, since it is larger than the sum of its proper divisors (1).

669661 is an equidigital number, since it uses as much as digits as its factorization.

669661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11664, while the sum is 34.

The square root of 669661 is about 818.3281737787. The cubic root of 669661 is about 87.4886407023.

The spelling of 669661 in words is "six hundred sixty-nine thousand, six hundred sixty-one".