15811381 has 2 divisors, whose sum is σ = 15811382. Its totient is φ = 15811380.

The previous prime is 15811379. The next prime is 15811391. The reversal of 15811381 is 18311851.

15811381 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13359025 + 2452356 = 3655^2 + 1566^2 .

It is a cyclic number.

It is not a de Polignac number, because 15811381 - 2¹ = 15811379 is a prime.

It is a super-2 number, since 2×15811381² = 499999538254322, which contains 22 as substring.

Together with 15811379, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15811391) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7905690 + 7905691.

It is an arithmetic number, because the mean of its divisors is an integer number (7905691).

Almost surely, 2^15811381 is an apocalyptic number.

It is an amenable number.

15811381 is a deficient number, since it is larger than the sum of its proper divisors (1).

15811381 is an equidigital number, since it uses as much as digits as its factorization.

15811381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 960, while the sum is 28.

The square root of 15811381 is about 3976.3527258029. The cubic root of 15811381 is about 250.9901055871.

The spelling of 15811381 in words is "fifteen million, eight hundred eleven thousand, three hundred eighty-one".