1221020220 has 144 divisors (see below), whose sum is σ = 3998937600. Its totient is φ = 277554816.

The previous prime is 1221020183. The next prime is 1221020231. The reversal of 1221020220 is 220201221.

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 = 1221020196 and 1221020205.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 584017 + ... + 586103.

It is an arithmetic number, because the mean of its divisors is an integer number (27770400).

Almost surely, 2^1221020220 is an apocalyptic number.

1221020220 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 1221020220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1999468800).

1221020220 is an abundant number, since it is smaller than the sum of its proper divisors (2777917380).

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

1221020220 is a wasteful number, since it uses less digits than its factorization.

1221020220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2312 (or 2303 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 12.

The square root of 1221020220 is about 34943.0997480189. The cubic root of 1221020220 is about 1068.8274983644.

Adding to 1221020220 its reverse (220201221), we get a palindrome (1441221441).

The spelling of 1221020220 in words is "one billion, two hundred twenty-one million, twenty thousand, two hundred twenty".