1221111220 has 24 divisors (see below), whose sum is σ = 2930667264. Its totient is φ = 418666656.

The previous prime is 1221111167. The next prime is 1221111253. The reversal of 1221111220 is 221111221.

It is a super-2 number, since 2×1221111220² = 2982225223219776800, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1221111220.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4360972 + ... + 4361251.

It is an arithmetic number, because the mean of its divisors is an integer number (122111136).

Almost surely, 2^1221111220 is an apocalyptic number.

1221111220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221111220 is an abundant number, since it is smaller than the sum of its proper divisors (1709556044).

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

1221111220 is a wasteful number, since it uses less digits than its factorization.

1221111220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8722239 (or 8722237 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 13.

The square root of 1221111220 is about 34944.4018406382. The cubic root of 1221111220 is about 1068.8540501731.

Adding to 1221111220 its reverse (221111221), we get a palindrome (1442222441).

Subtracting from 1221111220 its reverse (221111221), we obtain a palindrome (999999999).

The spelling of 1221111220 in words is "one billion, two hundred twenty-one million, one hundred eleven thousand, two hundred twenty".