21081685399 has 2 divisors, whose sum is σ = 21081685400. Its totient is φ = 21081685398.

The previous prime is 21081685381. The next prime is 21081685451. The reversal of 21081685399 is 99358618012.

It is an a-pointer prime, because the next prime (21081685451) can be obtained adding 21081685399 to its sum of digits (52).

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21081685399 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21081685319) 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, 10540842699 + 10540842700.

It is an arithmetic number, because the mean of its divisors is an integer number (10540842700).

Almost surely, 2^21081685399 is an apocalyptic number.

21081685399 is a deficient number, since it is larger than the sum of its proper divisors (1).

21081685399 is an equidigital number, since it uses as much as digits as its factorization.

21081685399 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 933120, while the sum is 52.

The spelling of 21081685399 in words is "twenty-one billion, eighty-one million, six hundred eighty-five thousand, three hundred ninety-nine".