21085664399 has 2 divisors, whose sum is σ = 21085664400. Its totient is φ = 21085664398.

The previous prime is 21085664393. The next prime is 21085664429. The reversal of 21085664399 is 99346658012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21085664399 - 2³² = 16790697103 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21085664399.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21085664393) 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, 10542832199 + 10542832200.

It is an arithmetic number, because the mean of its divisors is an integer number (10542832200).

Almost surely, 2^21085664399 is an apocalyptic number.

21085664399 is a deficient number, since it is larger than the sum of its proper divisors (1).

21085664399 is an equidigital number, since it uses as much as digits as its factorization.

21085664399 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2799360, while the sum is 53.

The spelling of 21085664399 in words is "twenty-one billion, eighty-five million, six hundred sixty-four thousand, three hundred ninety-nine".