663608781 has 20 divisors (see below), whose sum is σ = 1081437984. Its totient is φ = 402186600.

The previous prime is 663608773. The next prime is 663608789. The reversal of 663608781 is 187806366.

663608781 is a `hidden beast` number, since 6 + 636 + 0 + 8 + 7 + 8 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (663608773) and next prime (663608789).

It is not a de Polignac number, because 663608781 - 2³ = 663608773 is a prime.

It is a super-2 number, since 2×663608781² = 880753228440611922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (663608789) 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 in 19 ways as a sum of consecutive naturals, for example, 371505 + ... + 373286.

Almost surely, 2^663608781 is an apocalyptic number.

It is an amenable number.

663608781 is a deficient number, since it is larger than the sum of its proper divisors (417829203).

663608781 is a wasteful number, since it uses less digits than its factorization.

663608781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 744814 (or 744805 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 45.

The square root of 663608781 is about 25760.6052141637. The cubic root of 663608781 is about 872.2427627861.

The spelling of 663608781 in words is "six hundred sixty-three million, six hundred eight thousand, seven hundred eighty-one".