1221154105221 has 16 divisors (see below), whose sum is σ = 1871500545600. Its totient is φ = 786030228144.

The previous prime is 1221154105201. The next prime is 1221154105271. The reversal of 1221154105221 is 1225014511221.

1221154105221 is a `hidden beast` number, since 1 + 2 + 21 + 1 + 5 + 410 + 5 + 221 = 666.

It is not a de Polignac number, because 1221154105221 - 2¹⁰ = 1221154104197 is a prime.

It is a super-2 number, since 2×1221154105221² (a number of 25 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221154105201) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 779791111 + ... + 779792676.

It is an arithmetic number, because the mean of its divisors is an integer number (116968784100).

Almost surely, 2^{1221154105221} is an apocalyptic number.

It is an amenable number.

1221154105221 is a deficient number, since it is larger than the sum of its proper divisors (650346440379).

1221154105221 is a wasteful number, since it uses less digits than its factorization.

1221154105221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1559583825 (or 1559583819 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 27.

Adding to 1221154105221 its reverse (1225014511221), we get a palindrome (2446168616442).

The spelling of 1221154105221 in words is "one trillion, two hundred twenty-one billion, one hundred fifty-four million, one hundred five thousand, two hundred twenty-one".