1221021220 has 24 divisors (see below), whose sum is σ = 2652564600. Its totient is φ = 471566592.

The previous prime is 1221021203. The next prime is 1221021223. The reversal of 1221021220 is 221201221.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 19289664 + 1201731556 = 4392^2 + 34666^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 1221021220.

It is not an unprimeable number, because it can be changed into a prime (1221021223) 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 7 ways as a sum of consecutive naturals, for example, 1052025 + ... + 1053184.

It is an arithmetic number, because the mean of its divisors is an integer number (110523525).

Almost surely, 2^1221021220 is an apocalyptic number.

1221021220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221021220 is an abundant number, since it is smaller than the sum of its proper divisors (1431543380).

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

1221021220 is a wasteful number, since it uses less digits than its factorization.

1221021220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2105247 (or 2105245 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 1221021220 is about 34943.1140569927. The cubic root of 1221021220 is about 1068.8277901496.

Adding to 1221021220 its reverse (221201221), we get a palindrome (1442222441).

The spelling of 1221021220 in words is "one billion, two hundred twenty-one million, twenty-one thousand, two hundred twenty".