21365971853 has 2 divisors, whose sum is σ = 21365971854. Its totient is φ = 21365971852.

The previous prime is 21365971849. The next prime is 21365971871. The reversal of 21365971853 is 35817956312.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20898460969 + 467510884 = 144563^2 + 21622^2 .

It is a cyclic number.

It is not a de Polignac number, because 21365971853 - 2² = 21365971849 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21365971843) 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, 10682985926 + 10682985927.

It is an arithmetic number, because the mean of its divisors is an integer number (10682985927).

Almost surely, 2^21365971853 is an apocalyptic number.

It is an amenable number.

21365971853 is a deficient number, since it is larger than the sum of its proper divisors (1).

21365971853 is an equidigital number, since it uses as much as digits as its factorization.

21365971853 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1360800, while the sum is 50.

The spelling of 21365971853 in words is "twenty-one billion, three hundred sixty-five million, nine hundred seventy-one thousand, eight hundred fifty-three".