1221101220 has 24 divisors (see below), whose sum is σ = 3419083584. Its totient is φ = 325626976.

The previous prime is 1221101209. The next prime is 1221101221. The reversal of 1221101220 is 221011221.

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 = 1221101196 and 1221101205.

It is not an unprimeable number, because it can be changed into a prime (1221101221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10175784 + ... + 10175903.

It is an arithmetic number, because the mean of its divisors is an integer number (142461816).

Almost surely, 2^1221101220 is an apocalyptic number.

1221101220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221101220 is an abundant number, since it is smaller than the sum of its proper divisors (2197982364).

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

1221101220 is a wasteful number, since it uses less digits than its factorization.

1221101220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20351699 (or 20351697 counting only the distinct ones).

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

The square root of 1221101220 is about 34944.2587559101. The cubic root of 1221101220 is about 1068.8511324565.

Adding to 1221101220 its reverse (221011221), we get a palindrome (1442112441).

The spelling of 1221101220 in words is "one billion, two hundred twenty-one million, one hundred one thousand, two hundred twenty".