1221121121220 has 288 divisors, whose sum is σ = 4973294027520. Its totient is φ = 234220999680.

The previous prime is 1221121121153. The next prime is 1221121121237. The reversal of 1221121121220 is 221211211221.

1221121121220 is a `hidden beast` number, since 1 + 2 + 211 + 211 + 21 + 220 = 666.

It is a super-2 number, since 2×1221121121220² (a number of 25 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 1221121121193 and 1221121121202.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 3208435 + ... + 3568794.

It is an arithmetic number, because the mean of its divisors is an integer number (17268382040).

Almost surely, 2^{1221121121220} is an apocalyptic number.

1221121121220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1221121121220 is an abundant number, since it is smaller than the sum of its proper divisors (3752172906300).

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

1221121121220 is a wasteful number, since it uses less digits than its factorization.

1221121121220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6777275 (or 6777270 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 18.

Adding to 1221121121220 its reverse (221211211221), we get a palindrome (1442332332441).

Subtracting from 1221121121220 its reverse (221211211221), we obtain a palindrome (999909909999).

It can be divided in two parts, 1221121 and 121220, that added together give a triangular number (1342341 = T₁₆₃₈).

The spelling of 1221121121220 in words is "one trillion, two hundred twenty-one billion, one hundred twenty-one million, one hundred twenty-one thousand, two hundred twenty".