21020636993 has 2 divisors, whose sum is σ = 21020636994. Its totient is φ = 21020636992.

The previous prime is 21020636893. The next prime is 21020636999. The reversal of 21020636993 is 39963602012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20281177744 + 739459249 = 142412^2 + 27193^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020636993 - 2²⁰ = 21019588417 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21020636993.

It is not a weakly prime, because it can be changed into another prime (21020636999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510318496 + 10510318497.

It is an arithmetic number, because the mean of its divisors is an integer number (10510318497).

Almost surely, 2^21020636993 is an apocalyptic number.

It is an amenable number.

21020636993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020636993 is an equidigital number, since it uses as much as digits as its factorization.

21020636993 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 104976, while the sum is 41.

The spelling of 21020636993 in words is "twenty-one billion, twenty million, six hundred thirty-six thousand, nine hundred ninety-three".