13663781 has 2 divisors, whose sum is σ = 13663782. Its totient is φ = 13663780.

The previous prime is 13663763. The next prime is 13663787. The reversal of 13663781 is 18736631.

13663781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 8673025 + 4990756 = 2945^2 + 2234^2 .

It is a cyclic number.

It is not a de Polignac number, because 13663781 - 2¹⁰ = 13662757 is a prime.

It is a super-2 number, since 2×13663781² = 373397822431922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (13663787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6831890 + 6831891.

It is an arithmetic number, because the mean of its divisors is an integer number (6831891).

Almost surely, 2^13663781 is an apocalyptic number.

It is an amenable number.

13663781 is a deficient number, since it is larger than the sum of its proper divisors (1).

13663781 is an equidigital number, since it uses as much as digits as its factorization.

13663781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 35.

The square root of 13663781 is about 3696.4551938310. The cubic root of 13663781 is about 239.0692014383.

The spelling of 13663781 in words is "thirteen million, six hundred sixty-three thousand, seven hundred eighty-one".