21123608881 has 2 divisors, whose sum is σ = 21123608882. Its totient is φ = 21123608880.

The previous prime is 21123608873. The next prime is 21123608887. The reversal of 21123608881 is 18880632112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10979896225 + 10143712656 = 104785^2 + 100716^2 .

It is a cyclic number.

It is not a de Polignac number, because 21123608881 - 2³ = 21123608873 is a prime.

It is a super-2 number, since 2×21123608881² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21123608887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561804440 + 10561804441.

It is an arithmetic number, because the mean of its divisors is an integer number (10561804441).

Almost surely, 2^21123608881 is an apocalyptic number.

It is an amenable number.

21123608881 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123608881 is an equidigital number, since it uses as much as digits as its factorization.

21123608881 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36864, while the sum is 40.

The spelling of 21123608881 in words is "twenty-one billion, one hundred twenty-three million, six hundred eight thousand, eight hundred eighty-one".