81631 has 8 divisors (see below), whose sum is σ = 91728.
Its totient is φ = 72000.
The previous prime is 81629. The next prime is 81637. The reversal of 81631 is 13618.
It is a sphenic number, since it is the product of 3 distinct primes.
It is a 6-Lehmer number, since φ(81631) divides (81631-1)6.
It is a cyclic number.
It is not a de Polignac number, because 81631 - 21 = 81629 is a prime.
It is a super-2 number, since 2×816312 = 13327240322, which contains 22 as substring.
It is a Duffinian number.
It is a junction number, because it is equal to n+sod(n) for n = 81599 and 81608.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (81637) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (13) of ones.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 361 + ... + 541.
It is an arithmetic number, because the mean of its divisors is an integer number (11466).
281631 is an apocalyptic number.
81631 is the 181-st heptagonal number.
81631 is a deficient number, since it is larger than the sum of its proper divisors (10097).
81631 is a wasteful number, since it uses less digits than its factorization.
81631 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 233.
The product of its digits is 144, while the sum is 19.
The square root of 81631 is about 285.7113928425.
The cubic root of 81631 is about 43.3795496395.
The spelling of 81631 in words is "eighty-one thousand, six hundred thirty-one".