21615844841 has 2 divisors, whose sum is σ = 21615844842. Its totient is φ = 21615844840.

The previous prime is 21615844781. The next prime is 21615844867. The reversal of 21615844841 is 14844851612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20212593241 + 1403251600 = 142171^2 + 37460^2 .

It is a cyclic number.

It is not a de Polignac number, because 21615844841 - 2²⁶ = 21548735977 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21615844792 and 21615844801.

It is not a weakly prime, because it can be changed into another prime (21615843841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10807922420 + 10807922421.

It is an arithmetic number, because the mean of its divisors is an integer number (10807922421).

Almost surely, 2^21615844841 is an apocalyptic number.

It is an amenable number.

21615844841 is a deficient number, since it is larger than the sum of its proper divisors (1).

21615844841 is an equidigital number, since it uses as much as digits as its factorization.

21615844841 is an evil number, because the sum of its binary digits is even.

The product of its digits is 245760, while the sum is 44.

The spelling of 21615844841 in words is "twenty-one billion, six hundred fifteen million, eight hundred forty-four thousand, eight hundred forty-one".