12813781 has 4 divisors (see below), whose sum is σ = 12824064. Its totient is φ = 12803500.

The previous prime is 12813761. The next prime is 12813791. The reversal of 12813781 is 18731821.

It is a happy number.

12813781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 12813781 - 2⁷ = 12813653 is a prime.

It is a super-2 number, since 2×12813781² = 328385967031922, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (12813701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2965 + ... + 5866.

It is an arithmetic number, because the mean of its divisors is an integer number (3206016).

Almost surely, 2^12813781 is an apocalyptic number.

It is an amenable number.

12813781 is a deficient number, since it is larger than the sum of its proper divisors (10283).

12813781 is an equidigital number, since it uses as much as digits as its factorization.

12813781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10282.

The product of its digits is 2688, while the sum is 31.

The square root of 12813781 is about 3579.6341991885. The cubic root of 12813781 is about 234.0053387147.

The spelling of 12813781 in words is "twelve million, eight hundred thirteen thousand, seven hundred eighty-one".