1211111220 has 48 divisors (see below), whose sum is σ = 3699396288. Its totient is φ = 293602560.

The previous prime is 1211111201. The next prime is 1211111249. The reversal of 1211111220 is 221111121.

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 = 1211111196 and 1211111205.

It is a congruent number.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 916849 + ... + 918168.

It is an arithmetic number, because the mean of its divisors is an integer number (77070756).

Almost surely, 2^1211111220 is an apocalyptic number.

1211111220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1211111220 is an abundant number, since it is smaller than the sum of its proper divisors (2488285068).

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

1211111220 is a wasteful number, since it uses less digits than its factorization.

1211111220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1835040 (or 1835038 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 12.

The square root of 1211111220 is about 34801.0232608181. The cubic root of 1211111220 is about 1065.9283404081.

Adding to 1211111220 its reverse (221111121), we get a palindrome (1432222341).

Subtracting from 1211111220 its reverse (221111121), we obtain a palindrome (990000099).

The spelling of 1211111220 in words is "one billion, two hundred eleven million, one hundred eleven thousand, two hundred twenty".