21123385121 has 2 divisors, whose sum is σ = 21123385122. Its totient is φ = 21123385120.

The previous prime is 21123385111. The next prime is 21123385187. The reversal of 21123385121 is 12158332112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12684390625 + 8438994496 = 112625^2 + 91864^2 .

It is a cyclic number.

It is not a de Polignac number, because 21123385121 - 2⁶ = 21123385057 is a prime.

It is not a weakly prime, because it can be changed into another prime (21123385111) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561692560 + 10561692561.

It is an arithmetic number, because the mean of its divisors is an integer number (10561692561).

Almost surely, 2^21123385121 is an apocalyptic number.

It is an amenable number.

21123385121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123385121 is an equidigital number, since it uses as much as digits as its factorization.

21123385121 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2880, while the sum is 29.

The spelling of 21123385121 in words is "twenty-one billion, one hundred twenty-three million, three hundred eighty-five thousand, one hundred twenty-one".