21123301312181 has 2 divisors, whose sum is σ = 21123301312182. Its totient is φ = 21123301312180.

The previous prime is 21123301312163. The next prime is 21123301312219. The reversal of 21123301312181 is 18121310332112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18828179331025 + 2295121981156 = 4339145^2 + 1514966^2 .

It is a cyclic number.

It is not a de Polignac number, because 21123301312181 - 2³⁰ = 21122227570357 is a prime.

It is a super-2 number, since 2×21123301312181² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21123301312111) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561650656090 + 10561650656091.

It is an arithmetic number, because the mean of its divisors is an integer number (10561650656091).

Almost surely, 2^{21123301312181} is an apocalyptic number.

It is an amenable number.

21123301312181 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123301312181 is an equidigital number, since it uses as much as digits as its factorization.

21123301312181 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1728, while the sum is 29.

Adding to 21123301312181 its reverse (18121310332112), we get a palindrome (39244611644293).

The spelling of 21123301312181 in words is "twenty-one trillion, one hundred twenty-three billion, three hundred one million, three hundred twelve thousand, one hundred eighty-one".