663581 has 2 divisors, whose sum is σ = 663582. Its totient is φ = 663580.

The previous prime is 663571. The next prime is 663583. The reversal of 663581 is 185366.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 422500 + 241081 = 650^2 + 491^2 .

It is a cyclic number.

It is not a de Polignac number, because 663581 - 2⁶ = 663517 is a prime.

It is a super-2 number, since 2×663581² = 880679487122, which contains 22 as substring.

Together with 663583, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 663581.

It is not a weakly prime, because it can be changed into another prime (663583) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 331790 + 331791.

It is an arithmetic number, because the mean of its divisors is an integer number (331791).

663581 is a Friedman number, since it can be written as 6*((8*6)^3+5)-1, using all its digits and the basic arithmetic operations.

2⁶⁶³⁵⁸¹ is an apocalyptic number.

It is an amenable number.

663581 is a deficient number, since it is larger than the sum of its proper divisors (1).

663581 is an equidigital number, since it uses as much as digits as its factorization.

663581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 29.

The square root of 663581 is about 814.6048121635. The cubic root of 663581 is about 87.2230590899.

The spelling of 663581 in words is "six hundred sixty-three thousand, five hundred eighty-one".