81511331 has 16 divisors (see below), whose sum is σ = 91069440. Its totient is φ = 72334080.

The previous prime is 81511319. The next prime is 81511357. The reversal of 81511331 is 13311518.

It is a cyclic number.

It is not a de Polignac number, because 81511331 - 2¹⁰ = 81510307 is a prime.

It is a super-2 number, since 2×81511331² = 13288194162783122, which contains 22 as substring.

It is a plaindrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 81511297 and 81511306.

It is not an unprimeable number, because it can be changed into a prime (81511361) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 83810 + ... + 84776.

It is an arithmetic number, because the mean of its divisors is an integer number (5691840).

Almost surely, 2^81511331 is an apocalyptic number.

81511331 is a deficient number, since it is larger than the sum of its proper divisors (9558109).

81511331 is a wasteful number, since it uses less digits than its factorization.

81511331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1154.

The product of its digits is 360, while the sum is 23.

The square root of 81511331 is about 9028.3625868703. The cubic root of 81511331 is about 433.5834149504.

Adding to 81511331 its reverse (13311518), we get a palindrome (94822849).

The spelling of 81511331 in words is "eighty-one million, five hundred eleven thousand, three hundred thirty-one".