21212 is nontrivially palindromic in base 10.
21212 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.
It is a nude number because it is divisible by every one of its digits.
It is an alternating number because its digits alternate between even and odd.
21212 is an undulating number in base 10.
It is a nialpdrome in base 15.
It is a self number, because there is not a number n which added to its sum of digits gives 21212.
It is a congruent number.
221212 is an apocalyptic number.
It is an amenable number.
21212 is a wasteful number, since it uses less digits than its factorization.
21212 is an evil number, because the sum of its binary digits is even.
The square root of 21212 is about 145.6434001251. The cubic root of 21212 is about 27.6817710785.
The spelling of 21212 in words is "twenty-one thousand, two hundred twelve", and thus it is an iban number.