1211121220 has 12 divisors (see below), whose sum is σ = 2543354604. Its totient is φ = 484448480.

The previous prime is 1211121209. The next prime is 1211121227. The reversal of 1211121220 is 221211121.

It can be written as a sum of positive squares in 2 ways, for example, as 955057216 + 256064004 = 30904^2 + 16002^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 1211121220.

It is not an unprimeable number, because it can be changed into a prime (1211121227) 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 3 ways as a sum of consecutive naturals, for example, 30278011 + ... + 30278050.

It is an arithmetic number, because the mean of its divisors is an integer number (211946217).

Almost surely, 2^1211121220 is an apocalyptic number.

1211121220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1211121220 is an abundant number, since it is smaller than the sum of its proper divisors (1332233384).

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

1211121220 is a wasteful number, since it uses less digits than its factorization.

1211121220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60556070 (or 60556068 counting only the distinct ones).

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

The square root of 1211121220 is about 34801.1669344578. The cubic root of 1211121220 is about 1065.9312741475.

Adding to 1211121220 its reverse (221211121), we get a palindrome (1432332341).

The spelling of 1211121220 in words is "one billion, two hundred eleven million, one hundred twenty-one thousand, two hundred twenty".