1221011100100 has 288 divisors, whose sum is σ = 2967274582272. Its totient is φ = 432414720000.

The previous prime is 1221011100083. The next prime is 1221011100107. The reversal of 1221011100100 is 10011101221.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is not an unprimeable number, because it can be changed into a prime (1221011100107) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 2648613870 + ... + 2648614330.

It is an arithmetic number, because the mean of its divisors is an integer number (10303036744).

Almost surely, 2^{1221011100100} is an apocalyptic number.

1221011100100 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 1221011100100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1483637291136).

1221011100100 is an abundant number, since it is smaller than the sum of its proper divisors (1746263482172).

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

1221011100100 is a wasteful number, since it uses less digits than its factorization.

1221011100100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 927 (or 920 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 10.

Adding to 1221011100100 its reverse (10011101221), we get a palindrome (1231022201321).

The spelling of 1221011100100 in words is "one trillion, two hundred twenty-one billion, eleven million, one hundred thousand, one hundred".