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663 = 31317

663 has 8 divisors (see below), whose sum is σ = 1008. Its totient is φ = 384.

The previous prime is 661. The next prime is 673. The reversal of 663 is 366.

663 is an esthetic number in base 5, because in such base its adjacent digits differ by 1.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 663 - 21 = 661 is a prime.

It is a Smith number, since the sum of its digits (15) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a plaindrome in base 8 and base 14.

It is a nialpdrome in base 10 and base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31 + ... + 47.

It is an arithmetic number, because the mean of its divisors is an integer number (126).

663 is a deficient number, since it is larger than the sum of its proper divisors (345).

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

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

The sum of its prime factors is 33.

The product of its digits is 108, while the sum is 15.

The square root of 663 is about 25.7487863792. The cubic root of 663 is about 8.7197595535.

Subtracting from 663 its product of digits (108), we obtain a palindrome (555).

It can be divided in two parts, 6 and 63, that multiplied together give a triangular number (378 = T27).

The spelling of 663 in words is "six hundred sixty-three", and thus it is an aban number and an oban number.

Divisors: 1 3 13 17 39 51 221 663