664621 has 2 divisors, whose sum is σ = 664622. Its totient is φ = 664620.

The previous prime is 664619. The next prime is 664633. The reversal of 664621 is 126466.

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., 662596 + 2025 = 814^2 + 45^2 .

It is a cyclic number.

It is not a de Polignac number, because 664621 - 2¹ = 664619 is a prime.

Together with 664619, 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 (664661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332310 + 332311.

It is an arithmetic number, because the mean of its divisors is an integer number (332311).

2⁶⁶⁴⁶²¹ is an apocalyptic number.

It is an amenable number.

664621 is a deficient number, since it is larger than the sum of its proper divisors (1).

664621 is an equidigital number, since it uses as much as digits as its factorization.

664621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 25.

The square root of 664621 is about 815.2429085861. The cubic root of 664621 is about 87.2686022027.

The spelling of 664621 in words is "six hundred sixty-four thousand, six hundred twenty-one".