15691381 has 2 divisors, whose sum is σ = 15691382. Its totient is φ = 15691380.

The previous prime is 15691343. The next prime is 15691387. The reversal of 15691381 is 18319651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 9979281 + 5712100 = 3159^2 + 2390^2 .

It is a cyclic number.

It is not a de Polignac number, because 15691381 - 2⁷ = 15691253 is a prime.

It is a super-2 number, since 2×15691381² = 492438875374322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (15691387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7845690 + 7845691.

It is an arithmetic number, because the mean of its divisors is an integer number (7845691).

Almost surely, 2^15691381 is an apocalyptic number.

It is an amenable number.

15691381 is a deficient number, since it is larger than the sum of its proper divisors (1).

15691381 is an equidigital number, since it uses as much as digits as its factorization.

15691381 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6480, while the sum is 34.

The square root of 15691381 is about 3961.2347822365. The cubic root of 15691381 is about 250.3535318253.

The spelling of 15691381 in words is "fifteen million, six hundred ninety-one thousand, three hundred eighty-one".