13881781 has 2 divisors, whose sum is σ = 13881782. Its totient is φ = 13881780.

The previous prime is 13881773. The next prime is 13881787. The reversal of 13881781 is 18718831.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13439556 + 442225 = 3666^2 + 665^2 .

It is a cyclic number.

It is not a de Polignac number, because 13881781 - 2³ = 13881773 is a prime.

It is a super-2 number, since 2×13881781² = 385407687463922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 13881781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (13881787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6940890 + 6940891.

It is an arithmetic number, because the mean of its divisors is an integer number (6940891).

Almost surely, 2^13881781 is an apocalyptic number.

It is an amenable number.

13881781 is a deficient number, since it is larger than the sum of its proper divisors (1).

13881781 is an equidigital number, since it uses as much as digits as its factorization.

13881781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10752, while the sum is 37.

The square root of 13881781 is about 3725.8262170960. The cubic root of 13881781 is about 240.3339159887. Note that the first 3 decimals are identical.

The spelling of 13881781 in words is "thirteen million, eight hundred eighty-one thousand, seven hundred eighty-one".