1820 is nontrivially palindromic in base 9.
1820 is an esthetic number in base 8, because in such base its adjacent digits differ by 1.
1820 is an undulating number in base 8.
It is a nialpdrome in base 7, base 13 and base 14.
It is a zygodrome in base 2.
It is a congruent number.
1820 is an untouchable number, because it is not equal to the sum of proper divisors of any number.
21820 is an apocalyptic number.
1820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.
1820 is the 35-th pentagonal number.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 1820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2352).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
1820 is a wasteful number, since it uses less digits than its factorization.
1820 is an evil number, because the sum of its binary digits is even.
The square root of 1820 is about 42.6614580154. The cubic root of 1820 is about 12.2092914975.
The spelling of 1820 in words is "one thousand, eight hundred twenty".