13781609 has 4 divisors (see below), whose sum is σ = 13790340. Its totient is φ = 13772880.

The previous prime is 13781591. The next prime is 13781653. The reversal of 13781609 is 90618731.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 7997584 + 5784025 = 2828^2 + 2405^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-13781609 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (13781909) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1262 + ... + 5399.

It is an arithmetic number, because the mean of its divisors is an integer number (3447585).

Almost surely, 2^13781609 is an apocalyptic number.

It is an amenable number.

13781609 is a deficient number, since it is larger than the sum of its proper divisors (8731).

13781609 is an equidigital number, since it uses as much as digits as its factorization.

13781609 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8730.

The product of its (nonzero) digits is 9072, while the sum is 35.

The square root of 13781609 is about 3712.3589535496. The cubic root of 13781609 is about 239.7544305305.

The spelling of 13781609 in words is "thirteen million, seven hundred eighty-one thousand, six hundred nine".