13891721 has 2 divisors, whose sum is σ = 13891722. Its totient is φ = 13891720.

The previous prime is 13891699. The next prime is 13891729. The reversal of 13891721 is 12719831.

13891721 = 2635² + 2636².

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 6948496 + 6943225 = 2636^2 + 2635^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-13891721 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 (13891729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6945860 + 6945861.

It is an arithmetic number, because the mean of its divisors is an integer number (6945861).

Almost surely, 2^13891721 is an apocalyptic number.

13891721 is the 2636-th centered square number.

It is an amenable number.

13891721 is a deficient number, since it is larger than the sum of its proper divisors (1).

13891721 is an equidigital number, since it uses as much as digits as its factorization.

13891721 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3024, while the sum is 32.

The square root of 13891721 is about 3727.1599107095. The cubic root of 13891721 is about 240.3912657183.

The spelling of 13891721 in words is "thirteen million, eight hundred ninety-one thousand, seven hundred twenty-one".