1221100211221 has 48 divisors (see below), whose sum is σ = 1386555141888. Its totient is φ = 1065858393600.

The previous prime is 1221100211101. The next prime is 1221100211239. The reversal of 1221100211221 is 1221120011221.

It is not a de Polignac number, because 1221100211221 - 2²¹ = 1221098114069 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1221100211195 and 1221100211204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221100211251) 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, 1303201465 + ... + 1303202401.

It is an arithmetic number, because the mean of its divisors is an integer number (28886565456).

Almost surely, 2^{1221100211221} is an apocalyptic number.

1221100211221 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221100211221 is a deficient number, since it is larger than the sum of its proper divisors (165454930667).

1221100211221 is an equidigital number, since it uses as much as digits as its factorization.

1221100211221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1610 (or 1531 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 16.

Adding to 1221100211221 its reverse (1221120011221), we get a palindrome (2442220222442).

The spelling of 1221100211221 in words is "one trillion, two hundred twenty-one billion, one hundred million, two hundred eleven thousand, two hundred twenty-one".