21668598157693 has 2 divisors, whose sum is σ = 21668598157694. Its totient is φ = 21668598157692.

The previous prime is 21668598157673. The next prime is 21668598157751. The reversal of 21668598157693 is 39675189586612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12881624453604 + 8786973704089 = 3589098^2 + 2964283^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21668598157693 is a prime.

It is a super-2 number, since 2×21668598157693² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21668598157673) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10834299078846 + 10834299078847.

It is an arithmetic number, because the mean of its divisors is an integer number (10834299078847).

Almost surely, 2^{21668598157693} is an apocalyptic number.

It is an amenable number.

21668598157693 is a deficient number, since it is larger than the sum of its proper divisors (1).

21668598157693 is an equidigital number, since it uses as much as digits as its factorization.

21668598157693 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1175731200, while the sum is 76.

The spelling of 21668598157693 in words is "twenty-one trillion, six hundred sixty-eight billion, five hundred ninety-eight million, one hundred fifty-seven thousand, six hundred ninety-three".