81687 has 8 divisors (see below), whose sum is σ = 110704. Its totient is φ = 53568.

The previous prime is 81677. The next prime is 81689. The reversal of 81687 is 78618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81687 - 2⁴ = 81671 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 33 + ... + 405.

It is an arithmetic number, because the mean of its divisors is an integer number (13838).

2⁸¹⁶⁸⁷ is an apocalyptic number.

81687 is a deficient number, since it is larger than the sum of its proper divisors (29017).

81687 is a wasteful number, since it uses less digits than its factorization.

81687 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 449.

The product of its digits is 2688, while the sum is 30.

The square root of 81687 is about 285.8093770330. The cubic root of 81687 is about 43.3894670299.

It can be divided in two parts, 816 and 87, that added together give a triangular number (903 = T₄₂).

The spelling of 81687 in words is "eighty-one thousand, six hundred eighty-seven".