663618661 has 4 divisors (see below), whose sum is σ = 679804524. Its totient is φ = 647432800.

The previous prime is 663618653. The next prime is 663618667. The reversal of 663618661 is 166816366.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 118396161 + 545222500 = 10881^2 + 23350^2 .

It is a cyclic number.

It is not a de Polignac number, because 663618661 - 2³ = 663618653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (663618667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8092870 + ... + 8092951.

It is an arithmetic number, because the mean of its divisors is an integer number (169951131).

Almost surely, 2^663618661 is an apocalyptic number.

It is an amenable number.

663618661 is a deficient number, since it is larger than the sum of its proper divisors (16185863).

663618661 is a wasteful number, since it uses less digits than its factorization.

663618661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16185862.

The product of its digits is 186624, while the sum is 43.

The square root of 663618661 is about 25760.7969791309. The cubic root of 663618661 is about 872.2470914990.

The spelling of 663618661 in words is "six hundred sixty-three million, six hundred eighteen thousand, six hundred sixty-one".