Adding to 20420 its reverse (2402), we get a palindrome (22822).
It is a nialpdrome in base 12.
It is a congruent number.
It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 20420.
It is an unprimeable number.
20420 is an untouchable number, because it is not equal to the sum of proper divisors of any number.
220420 is an apocalyptic number.
20420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.
It is an amenable number.
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
20420 is a wasteful number, since it uses less digits than its factorization.
20420 is an evil number, because the sum of its binary digits is even.
The square root of 20420 is about 142.8985654232. The cubic root of 20420 is about 27.3328706379.
The spelling of 20420 in words is "twenty thousand, four hundred twenty", and thus it is an iban number.