81851131 has 2 divisors, whose sum is σ = 81851132. Its totient is φ = 81851130.

The previous prime is 81851117. The next prime is 81851149. The reversal of 81851131 is 13115818.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81851131 - 2⁹ = 81850619 is a prime.

It is a super-2 number, since 2×81851131² = 13399215291958322, 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 81851131.

It is not a weakly prime, because it can be changed into another prime (81851101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40925565 + 40925566.

It is an arithmetic number, because the mean of its divisors is an integer number (40925566).

Almost surely, 2^81851131 is an apocalyptic number.

81851131 is a deficient number, since it is larger than the sum of its proper divisors (1).

81851131 is an equidigital number, since it uses as much as digits as its factorization.

81851131 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 81851131 is about 9047.1614885554. The cubic root of 81851131 is about 434.1850793081.

Adding to 81851131 its reverse (13115818), we get a palindrome (94966949).

It can be divided in two parts, 8185 and 1131, that added together give a triangular number (9316 = T₁₃₆).

The spelling of 81851131 in words is "eighty-one million, eight hundred fifty-one thousand, one hundred thirty-one".