81231687 has 64 divisors (see below), whose sum is σ = 132689920. Its totient is φ = 48988800.

The previous prime is 81231679. The next prime is 81231737. The reversal of 81231687 is 78613218.

It is not a de Polignac number, because 81231687 - 2³ = 81231679 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81231617) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1331637 + ... + 1331697.

It is an arithmetic number, because the mean of its divisors is an integer number (2073280).

Almost surely, 2^81231687 is an apocalyptic number.

81231687 is a deficient number, since it is larger than the sum of its proper divisors (51458233).

81231687 is a wasteful number, since it uses less digits than its factorization.

81231687 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181 (or 175 counting only the distinct ones).

The product of its digits is 16128, while the sum is 36.

The square root of 81231687 is about 9012.8623089449. The cubic root of 81231687 is about 433.0870098423.

It can be divided in two parts, 81231 and 687, that added together give a palindrome (81918).

The spelling of 81231687 in words is "eighty-one million, two hundred thirty-one thousand, six hundred eighty-seven".