13939781 has 4 divisors (see below), whose sum is σ = 14168364. Its totient is φ = 13711200.

The previous prime is 13939769. The next prime is 13939831. The reversal of 13939781 is 18793931.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 18793931 = 13 ⋅1445687.

It can be written as a sum of positive squares in 2 ways, for example, as 4879681 + 9060100 = 2209^2 + 3010^2 .

It is a cyclic number.

It is not a de Polignac number, because 13939781 - 2¹⁴ = 13923397 is a prime.

It is a super-2 number, since 2×13939781² = 388634988655922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (13939721) 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, 114200 + ... + 114321.

It is an arithmetic number, because the mean of its divisors is an integer number (3542091).

Almost surely, 2^13939781 is an apocalyptic number.

It is an amenable number.

13939781 is a deficient number, since it is larger than the sum of its proper divisors (228583).

13939781 is an equidigital number, since it uses as much as digits as its factorization.

13939781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 228582.

The product of its digits is 40824, while the sum is 41.

The square root of 13939781 is about 3733.6016123845. The cubic root of 13939781 is about 240.6681670124.

The spelling of 13939781 in words is "thirteen million, nine hundred thirty-nine thousand, seven hundred eighty-one".