1221011220 has 192 divisors, whose sum is σ = 4059175680. Its totient is φ = 270336000.

The previous prime is 1221011177. The next prime is 1221011221. The reversal of 1221011220 is 221101221.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a junction number, because it is equal to n+sod(n) for n = 1221011196 and 1221011205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221011221) by changing a digit.

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 63 ways as a sum of consecutive naturals, for example, 865876 + ... + 867284.

It is an arithmetic number, because the mean of its divisors is an integer number (21141540).

Almost surely, 2^1221011220 is an apocalyptic number.

1221011220 is a gapful number since it is divisible by the number (10) 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 1221011220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2029587840).

1221011220 is an abundant number, since it is smaller than the sum of its proper divisors (2838164460).

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

1221011220 is a wasteful number, since it uses less digits than its factorization.

1221011220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1546 (or 1544 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

The square root of 1221011220 is about 34942.9709669913. The cubic root of 1221011220 is about 1068.8248722896.

Adding to 1221011220 its reverse (221101221), we get a palindrome (1442112441).

Subtracting from 1221011220 its reverse (221101221), we obtain a palindrome (999909999).

It can be divided in two parts, 122101 and 1220, that added together give a palindrome (123321).

The spelling of 1221011220 in words is "one billion, two hundred twenty-one million, eleven thousand, two hundred twenty".