664661 has 2 divisors, whose sum is σ = 664662. Its totient is φ = 664660.

The previous prime is 664633. The next prime is 664663. The reversal of 664661 is 166466.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 630436 + 34225 = 794^2 + 185^2 .

It is a cyclic number.

It is not a de Polignac number, because 664661 - 2⁶ = 664597 is a prime.

Together with 664663, 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 (664663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332330 + 332331.

It is an arithmetic number, because the mean of its divisors is an integer number (332331).

2⁶⁶⁴⁶⁶¹ is an apocalyptic number.

It is an amenable number.

664661 is a deficient number, since it is larger than the sum of its proper divisors (1).

664661 is an equidigital number, since it uses as much as digits as its factorization.

664661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 29.

The square root of 664661 is about 815.2674407825. The cubic root of 664661 is about 87.2703529118.

The spelling of 664661 in words is "six hundred sixty-four thousand, six hundred sixty-one".