663665021 has 2 divisors, whose sum is σ = 663665022. Its totient is φ = 663665020.

The previous prime is 663665011. The next prime is 663665059. The reversal of 663665021 is 120566366.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 558376900 + 105288121 = 23630^2 + 10261^2 .

It is a cyclic number.

It is not a de Polignac number, because 663665021 - 2¹⁴ = 663648637 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (663665011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 331832510 + 331832511.

It is an arithmetic number, because the mean of its divisors is an integer number (331832511).

Almost surely, 2^663665021 is an apocalyptic number.

It is an amenable number.

663665021 is a deficient number, since it is larger than the sum of its proper divisors (1).

663665021 is an equidigital number, since it uses as much as digits as its factorization.

663665021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 38880, while the sum is 35.

The square root of 663665021 is about 25761.6967802977. The cubic root of 663665021 is about 872.2674025782.

The spelling of 663665021 in words is "six hundred sixty-three million, six hundred sixty-five thousand, twenty-one".