21664252543993 has 2 divisors, whose sum is σ = 21664252543994. Its totient is φ = 21664252543992.

The previous prime is 21664252543963. The next prime is 21664252544059. The reversal of 21664252543993 is 39934525246612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21261247224064 + 403005319929 = 4610992^2 + 634827^2 .

It is a cyclic number.

It is not a de Polignac number, because 21664252543993 - 2¹³ = 21664252535801 is a prime.

It is not a weakly prime, because it can be changed into another prime (21664252543963) 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, 10832126271996 + 10832126271997.

It is an arithmetic number, because the mean of its divisors is an integer number (10832126271997).

Almost surely, 2^{21664252543993} is an apocalyptic number.

It is an amenable number.

21664252543993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21664252543993 is an equidigital number, since it uses as much as digits as its factorization.

21664252543993 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 83980800, while the sum is 61.

The spelling of 21664252543993 in words is "twenty-one trillion, six hundred sixty-four billion, two hundred fifty-two million, five hundred forty-three thousand, nine hundred ninety-three".