20421220 has 48 divisors (see below), whose sum is σ = 44861040. Its totient is φ = 7798784.

The previous prime is 20421209. The next prime is 20421223. The reversal of 20421220 is 2212402.

It can be written as a sum of positive squares in 8 ways, for example, as 1965604 + 18455616 = 1402^2 + 4296^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 20421220.

It is not an unprimeable number, because it can be changed into a prime (20421223) by changing a digit.

It is a nontrivial repunit in base 273.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 79332 + ... + 79588.

It is an arithmetic number, because the mean of its divisors is an integer number (934605).

Almost surely, 2^20421220 is an apocalyptic number.

20421220 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 practical number, because each smaller number is the sum of distinct divisors of 20421220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22430520).

20421220 is an abundant number, since it is smaller than the sum of its proper divisors (24439820).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20421220 is a wasteful number, since it uses less digits than its factorization.

20421220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 432 (or 430 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 13.

The square root of 20421220 is about 4518.9843991764. The cubic root of 20421220 is about 273.3341496439.

Adding to 20421220 its reverse (2212402), we get a palindrome (22633622).

The spelling of 20421220 in words is "twenty million, four hundred twenty-one thousand, two hundred twenty".