81000 has 80 divisors (see below), whose sum is σ = 283140.
Its totient is φ = 21600.
The previous prime is 80989. The next prime is 81001. The reversal of 81000 is 18.
Adding to 81000 its reverse (18), we get a palindrome (81018).
It is a powerful number, because all its prime factors have an exponent greater than 1
and also an Achilles number because it is not a perfect power.
It can be written as a sum of positive squares in 2 ways, for example, as 54756 + 26244 = 234^2 + 162^2
It is an ABA number since it can be written as A⋅BA, here for A=3, B=30.
It is a super-2 number, since 2×810002 = 13122000000, which contains 22 as substring.
It is a Harshad number since it is a multiple of its sum of digits (9).
It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.
It is a nialpdrome in base 10.
It is not an unprimeable number, because it can be changed into a prime (81001) by changing a digit.
It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 16198 + ... + 16202.
281000 is an apocalyptic number.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 81000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (141570).
81000 is an abundant number, since it is smaller than the sum of its proper divisors (202140).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
81000 is a wasteful number, since it uses less digits than its factorization.
81000 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 33 (or 10 counting only the distinct ones).
The product of its (nonzero) digits is 8, while the sum is 9.
The square root of 81000 is about 284.6049894152.
The cubic root of 81000 is about 43.2674871092.
The spelling of 81000 in words is "eighty-one thousand".