1211221220 has 24 divisors (see below), whose sum is σ = 2774798208. Its totient is φ = 440444000.

The previous prime is 1211221213. The next prime is 1211221237. The reversal of 1211221220 is 221221121.

It is a junction number, because it is equal to n+sod(n) for n = 1211221195 and 1211221204.

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, 2752556 + ... + 2752995.

It is an arithmetic number, because the mean of its divisors is an integer number (115616592).

Almost surely, 2^1211221220 is an apocalyptic number.

1211221220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1211221220 is an abundant number, since it is smaller than the sum of its proper divisors (1563576988).

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

1211221220 is a wasteful number, since it uses less digits than its factorization.

1211221220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5505571 (or 5505569 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 14.

The square root of 1211221220 is about 34802.6036382337. The cubic root of 1211221220 is about 1065.9606106532.

Adding to 1211221220 its reverse (221221121), we get a palindrome (1432442341).

Subtracting from 1211221220 its reverse (221221121), we obtain a palindrome (990000099).

The spelling of 1211221220 in words is "one billion, two hundred eleven million, two hundred twenty-one thousand, two hundred twenty".