81131787 has 80 divisors (see below), whose sum is σ = 143016192. Its totient is φ = 45334080.

The previous prime is 81131779. The next prime is 81131789. The reversal of 81131787 is 78713118.

It is not a de Polignac number, because 81131787 - 2³ = 81131779 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81131789) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 758188 + ... + 758294.

Almost surely, 2^81131787 is an apocalyptic number.

81131787 is a deficient number, since it is larger than the sum of its proper divisors (61884405).

81131787 is a wasteful number, since it uses less digits than its factorization.

81131787 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 190 (or 181 counting only the distinct ones).

The product of its digits is 9408, while the sum is 36.

The square root of 81131787 is about 9007.3185244000. The cubic root of 81131787 is about 432.9093979515.

It can be divided in two parts, 81131 and 787, that added together give a palindrome (81918).

The spelling of 81131787 in words is "eighty-one million, one hundred thirty-one thousand, seven hundred eighty-seven".