1211221220100 has 144 divisors (see below), whose sum is σ = 3529568759808. Its totient is φ = 320686623360.

The previous prime is 1211221220023. The next prime is 1211221220107. The reversal of 1211221220100 is 10221221121.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 1211221220100.

It is not an unprimeable number, because it can be changed into a prime (1211221220107) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 24968469 + ... + 25016931.

Almost surely, 2^{1211221220100} is an apocalyptic number.

1211221220100 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 1211221220100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1764784379904).

1211221220100 is an abundant number, since it is smaller than the sum of its proper divisors (2318347539708).

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

1211221220100 is a wasteful number, since it uses less digits than its factorization.

1211221220100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 49074 (or 49067 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 1211221220100 its reverse (10221221121), we get a palindrome (1221442441221).

The spelling of 1211221220100 in words is "one trillion, two hundred eleven billion, two hundred twenty-one million, two hundred twenty thousand, one hundred".