21243240617 has 2 divisors, whose sum is σ = 21243240618. Its totient is φ = 21243240616.

The previous prime is 21243240607. The next prime is 21243240619. The reversal of 21243240617 is 71604234212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20961537961 + 281702656 = 144781^2 + 16784^2 .

It is a cyclic number.

It is not a de Polignac number, because 21243240617 - 2¹⁶ = 21243175081 is a prime.

Together with 21243240619, 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 (21243240619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621620308 + 10621620309.

It is an arithmetic number, because the mean of its divisors is an integer number (10621620309).

Almost surely, 2^21243240617 is an apocalyptic number.

It is an amenable number.

21243240617 is a deficient number, since it is larger than the sum of its proper divisors (1).

21243240617 is an equidigital number, since it uses as much as digits as its factorization.

21243240617 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16128, while the sum is 32.

Adding to 21243240617 its reverse (71604234212), we get a palindrome (92847474829).

The spelling of 21243240617 in words is "twenty-one billion, two hundred forty-three million, two hundred forty thousand, six hundred seventeen".