1221211220 has 48 divisors (see below), whose sum is σ = 2680207488. Its totient is φ = 466519680.

The previous prime is 1221211181. The next prime is 1221211231. The reversal of 1221211220 is 221121221.

It is a junction number, because it is equal to n+sod(n) for n = 1221211195 and 1221211204.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 364955 + ... + 368285.

It is an arithmetic number, because the mean of its divisors is an integer number (55837656).

Almost surely, 2^1221211220 is an apocalyptic number.

1221211220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1221211220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1340103744).

1221211220 is an abundant number, since it is smaller than the sum of its proper divisors (1458996268).

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

1221211220 is a wasteful number, since it uses less digits than its factorization.

1221211220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4160 (or 4158 counting only the distinct ones).

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

The square root of 1221211220 is about 34945.8326556973. The cubic root of 1221211220 is about 1068.8832264637.

Adding to 1221211220 its reverse (221121221), we get a palindrome (1442332441).

It can be divided in two parts, 12212 and 11220, that added together give a palindrome (23432).

The spelling of 1221211220 in words is "one billion, two hundred twenty-one million, two hundred eleven thousand, two hundred twenty".