21742624735721 has 2 divisors, whose sum is σ = 21742624735722. Its totient is φ = 21742624735720.

The previous prime is 21742624735717. The next prime is 21742624735723. The reversal of 21742624735721 is 12753742624712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17236073173225 + 4506551562496 = 4151635^2 + 2122864^2 .

It is a cyclic number.

It is not a de Polignac number, because 21742624735721 - 2² = 21742624735717 is a prime.

Together with 21742624735723, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21742624735723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10871312367860 + 10871312367861.

It is an arithmetic number, because the mean of its divisors is an integer number (10871312367861).

Almost surely, 2^{21742624735721} is an apocalyptic number.

It is an amenable number.

21742624735721 is a deficient number, since it is larger than the sum of its proper divisors (1).

21742624735721 is an equidigital number, since it uses as much as digits as its factorization.

21742624735721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7902720, while the sum is 53.

The spelling of 21742624735721 in words is "twenty-one trillion, seven hundred forty-two billion, six hundred twenty-four million, seven hundred thirty-five thousand, seven hundred twenty-one".