21545554343121 has 12 divisors (see below), whose sum is σ = 31195278740340. Its totient is φ = 14329584833760.

The previous prime is 21545554343111. The next prime is 21545554343143. The reversal of 21545554343121 is 12134345554512.

21545554343121 is a `hidden beast` number, since 2 + 1 + 5 + 4 + 55 + 543 + 4 + 31 + 21 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 827481315600 + 20718073027521 = 909660^2 + 4551711^2 .

It is not a de Polignac number, because 21545554343121 - 2¹⁸ = 21545554080977 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21545554343111) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2843167806 + ... + 2843175383.

It is an arithmetic number, because the mean of its divisors is an integer number (2599606561695).

Almost surely, 2^{21545554343121} is an apocalyptic number.

It is an amenable number.

21545554343121 is a deficient number, since it is larger than the sum of its proper divisors (9649724397219).

21545554343121 is a wasteful number, since it uses less digits than its factorization.

21545554343121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5686343616 (or 5686343613 counting only the distinct ones).

The product of its digits is 1440000, while the sum is 45.

Adding to 21545554343121 its reverse (12134345554512), we get a palindrome (33679899897633).

The spelling of 21545554343121 in words is "twenty-one trillion, five hundred forty-five billion, five hundred fifty-four million, three hundred forty-three thousand, one hundred twenty-one".