81131751 has 6 divisors (see below), whose sum is σ = 117190320. Its totient is φ = 54087828.

The previous prime is 81131747. The next prime is 81131779. The reversal of 81131751 is 15713118.

It is not a de Polignac number, because 81131751 - 2² = 81131747 is a prime.

It is a super-2 number, since 2×81131751² = 13164722040652002, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81131731) 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 in 5 ways as a sum of consecutive naturals, for example, 4507311 + ... + 4507328.

It is an arithmetic number, because the mean of its divisors is an integer number (19531720).

Almost surely, 2^81131751 is an apocalyptic number.

81131751 is a deficient number, since it is larger than the sum of its proper divisors (36058569).

81131751 is a wasteful number, since it uses less digits than its factorization.

81131751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9014645 (or 9014642 counting only the distinct ones).

The product of its digits is 840, while the sum is 27.

The square root of 81131751 is about 9007.3165260248. The cubic root of 81131751 is about 432.9093339210.

Adding to 81131751 its reverse (15713118), we get a palindrome (96844869).

The spelling of 81131751 in words is "eighty-one million, one hundred thirty-one thousand, seven hundred fifty-one".