21220 has 12 divisors (see below), whose sum is σ = 44604.
Its totient is φ = 8480.
The previous prime is 21211. The next prime is 21221. The reversal of 21220 is 2212.
21220 = T101 + T102 + ... +
It is a happy number.
21220 is nontrivially palindromic in base 11.
It can be written as a sum of positive squares in 2 ways, for example, as 10816 + 10404 = 104^2 + 102^2
It is an Ulam number.
It is a nialpdrome in base 13.
It is not an unprimeable number, because it can be changed into a prime (21221) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (7) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 511 + ... + 550.
It is an arithmetic number, because the mean of its divisors is an integer number (3717).
221220 is an apocalyptic number.
21220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.
It is an amenable number.
21220 is an abundant number, since it is smaller than the sum of its proper divisors (23384).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22302).
21220 is a wasteful number, since it uses less digits than its factorization.
21220 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 1070 (or 1068 counting only the distinct ones).
The product of its (nonzero) digits is 8, while the sum is 7.
The square root of 21220 is about 145.6708618770.
The cubic root of 21220 is about 27.6852506551.
Adding to 21220 its reverse (2212), we get a palindrome (23432).
It can be divided in two parts, 212 and 20, that added together give a palindrome (232).
The spelling of 21220 in words is "twenty-one thousand, two hundred twenty", and thus it is an iban number.