663625621 has 2 divisors, whose sum is σ = 663625622. Its totient is φ = 663625620.

The previous prime is 663625619. The next prime is 663625639. The reversal of 663625621 is 126526366.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 421480900 + 242144721 = 20530^2 + 15561^2 .

It is a cyclic number.

It is not a de Polignac number, because 663625621 - 2¹ = 663625619 is a prime.

Together with 663625619, it forms a pair of twin primes.

It is equal to p_34464844 and since 663625621 and 34464844 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (663625121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 331812810 + 331812811.

It is an arithmetic number, because the mean of its divisors is an integer number (331812811).

Almost surely, 2^663625621 is an apocalyptic number.

It is an amenable number.

663625621 is a deficient number, since it is larger than the sum of its proper divisors (1).

663625621 is an equidigital number, since it uses as much as digits as its factorization.

663625621 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 77760, while the sum is 37.

The square root of 663625621 is about 25760.9320677649. The cubic root of 663625621 is about 872.2501408499.

The spelling of 663625621 in words is "six hundred sixty-three million, six hundred twenty-five thousand, six hundred twenty-one".