1221001220 has 48 divisors (see below), whose sum is σ = 2596321728. Its totient is φ = 482302080.

The previous prime is 1221001189. The next prime is 1221001261. The reversal of 1221001220 is 221001221.

It is a happy 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, 593714 + ... + 595766.

It is an arithmetic number, because the mean of its divisors is an integer number (54090036).

Almost surely, 2^1221001220 is an apocalyptic number.

1221001220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221001220 is an abundant number, since it is smaller than the sum of its proper divisors (1375320508).

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

1221001220 is a wasteful number, since it uses less digits than its factorization.

1221001220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2420 (or 2418 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 1221001220 is about 34942.8278764041. The cubic root of 1221001220 is about 1068.8219544136.

Adding to 1221001220 its reverse (221001221), we get a palindrome (1442002441).

Subtracting from 1221001220 its reverse (221001221), we obtain a palindrome (999999999).

It can be divided in two parts, 1221001 and 220, that added together give a palindrome (1221221).

The spelling of 1221001220 in words is "one billion, two hundred twenty-one million, one thousand, two hundred twenty".