663390661 has 2 divisors, whose sum is σ = 663390662. Its totient is φ = 663390660.

The previous prime is 663390659. The next prime is 663390683. The reversal of 663390661 is 166093366.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 602457025 + 60933636 = 24545^2 + 7806^2 .

It is a cyclic number.

It is not a de Polignac number, because 663390661 - 2¹ = 663390659 is a prime.

Together with 663390659, 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 (663390361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 331695330 + 331695331.

It is an arithmetic number, because the mean of its divisors is an integer number (331695331).

Almost surely, 2^663390661 is an apocalyptic number.

It is an amenable number.

663390661 is a deficient number, since it is larger than the sum of its proper divisors (1).

663390661 is an equidigital number, since it uses as much as digits as its factorization.

663390661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 104976, while the sum is 40.

The square root of 663390661 is about 25756.3712700372. The cubic root of 663390661 is about 872.1471871772.

The spelling of 663390661 in words is "six hundred sixty-three million, three hundred ninety thousand, six hundred sixty-one".