21553544332121 has 2 divisors, whose sum is σ = 21553544332122. Its totient is φ = 21553544332120.

The previous prime is 21553544332051. The next prime is 21553544332123. The reversal of 21553544332121 is 12123344535512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13178678760025 + 8374865572096 = 3630245^2 + 2893936^2 .

It is a cyclic number.

It is not a de Polignac number, because 21553544332121 - 2¹⁸ = 21553544069977 is a prime.

Together with 21553544332123, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21553544332123) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10776772166060 + 10776772166061.

It is an arithmetic number, because the mean of its divisors is an integer number (10776772166061).

Almost surely, 2^{21553544332121} is an apocalyptic number.

It is an amenable number.

21553544332121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21553544332121 is an equidigital number, since it uses as much as digits as its factorization.

21553544332121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 432000, while the sum is 41.

Adding to 21553544332121 its reverse (12123344535512), we get a palindrome (33676888867633).

The spelling of 21553544332121 in words is "twenty-one trillion, five hundred fifty-three billion, five hundred forty-four million, three hundred thirty-two thousand, one hundred twenty-one".