1213121221221 has 64 divisors (see below), whose sum is σ = 2115070272000. Its totient is φ = 601124944896.

The previous prime is 1213121221217. The next prime is 1213121221231. The reversal of 1213121221221 is 1221221213121.

It is not a de Polignac number, because 1213121221221 - 2² = 1213121221217 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1213121221231) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1777746 + ... + 2363603.

It is an arithmetic number, because the mean of its divisors is an integer number (33047973000).

Almost surely, 2^{1213121221221} is an apocalyptic number.

It is an amenable number.

1213121221221 is a deficient number, since it is larger than the sum of its proper divisors (901949050779).

1213121221221 is a wasteful number, since it uses less digits than its factorization.

1213121221221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4141438.

The product of its digits is 192, while the sum is 21.

Adding to 1213121221221 its reverse (1221221213121), we get a palindrome (2434342434342).

The spelling of 1213121221221 in words is "one trillion, two hundred thirteen billion, one hundred twenty-one million, two hundred twenty-one thousand, two hundred twenty-one".