1221001100 has 72 divisors (see below), whose sum is σ = 2909980416. Its totient is φ = 441000000.

The previous prime is 1221001097. The next prime is 1221001127. The reversal of 1221001100 is 11001221.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 162425 + ... + 169775.

Almost surely, 2^1221001100 is an apocalyptic number.

1221001100 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 1221001100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1454990208).

1221001100 is an abundant number, since it is smaller than the sum of its proper divisors (1688979316).

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

1221001100 is a wasteful number, since it uses less digits than its factorization.

1221001100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7527 (or 7520 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 8.

The square root of 1221001100 is about 34942.8261593134. The cubic root of 1221001100 is about 1068.8219193990.

Adding to 1221001100 its reverse (11001221), we get a palindrome (1232002321).

The spelling of 1221001100 in words is "one billion, two hundred twenty-one million, one thousand, one hundred".