21255354123161 has 2 divisors, whose sum is σ = 21255354123162. Its totient is φ = 21255354123160.

The previous prime is 21255354123131. The next prime is 21255354123193. The reversal of 21255354123161 is 16132145355212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13496483147536 + 7758870975625 = 3673756^2 + 2785475^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21255354123161 is a prime.

It is not a weakly prime, because it can be changed into another prime (21255354123131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10627677061580 + 10627677061581.

It is an arithmetic number, because the mean of its divisors is an integer number (10627677061581).

Almost surely, 2^{21255354123161} is an apocalyptic number.

It is an amenable number.

21255354123161 is a deficient number, since it is larger than the sum of its proper divisors (1).

21255354123161 is an equidigital number, since it uses as much as digits as its factorization.

21255354123161 is an evil number, because the sum of its binary digits is even.

The product of its digits is 216000, while the sum is 41.

Adding to 21255354123161 its reverse (16132145355212), we get a palindrome (37387499478373).

The spelling of 21255354123161 in words is "twenty-one trillion, two hundred fifty-five billion, three hundred fifty-four million, one hundred twenty-three thousand, one hundred sixty-one".