13781321 has 2 divisors, whose sum is σ = 13781322. Its totient is φ = 13781320.

The previous prime is 13781311. The next prime is 13781357. The reversal of 13781321 is 12318731.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11022400 + 2758921 = 3320^2 + 1661^2 .

It is a cyclic number.

It is not a de Polignac number, because 13781321 - 2¹⁰ = 13780297 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (13781311) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6890660 + 6890661.

It is an arithmetic number, because the mean of its divisors is an integer number (6890661).

Almost surely, 2^13781321 is an apocalyptic number.

It is an amenable number.

13781321 is a deficient number, since it is larger than the sum of its proper divisors (1).

13781321 is an equidigital number, since it uses as much as digits as its factorization.

13781321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1008, while the sum is 26.

The square root of 13781321 is about 3712.3201639945. The cubic root of 13781321 is about 239.7527604362.

The spelling of 13781321 in words is "thirteen million, seven hundred eighty-one thousand, three hundred twenty-one".