21263666165597 has 2 divisors, whose sum is σ = 21263666165598. Its totient is φ = 21263666165596.

The previous prime is 21263666165569. The next prime is 21263666165611. The reversal of 21263666165597 is 79556166636212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17448281368996 + 3815384796601 = 4177114^2 + 1953301^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21263666165597 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21263666165297) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10631833082798 + 10631833082799.

It is an arithmetic number, because the mean of its divisors is an integer number (10631833082799).

Almost surely, 2^{21263666165597} is an apocalyptic number.

It is an amenable number.

21263666165597 is a deficient number, since it is larger than the sum of its proper divisors (1).

21263666165597 is an equidigital number, since it uses as much as digits as its factorization.

21263666165597 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 146966400, while the sum is 65.

The spelling of 21263666165597 in words is "twenty-one trillion, two hundred sixty-three billion, six hundred sixty-six million, one hundred sixty-five thousand, five hundred ninety-seven".