1221311100 has 36 divisors (see below), whose sum is σ = 3533660984. Its totient is φ = 325682880.

The previous prime is 1221311081. The next prime is 1221311107. The reversal of 1221311100 is 11131221.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221311107) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 2035219 + ... + 2035818.

Almost surely, 2^1221311100 is an apocalyptic number.

1221311100 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221311100 is an abundant number, since it is smaller than the sum of its proper divisors (2312349884).

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

1221311100 is a wasteful number, since it uses less digits than its factorization.

1221311100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4071054 (or 4071047 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 12.

The square root of 1221311100 is about 34947.2616953031. The cubic root of 1221311100 is about 1068.9123661529.

Adding to 1221311100 its reverse (11131221), we get a palindrome (1232442321).

The spelling of 1221311100 in words is "one billion, two hundred twenty-one million, three hundred eleven thousand, one hundred".