16821999 has 10 divisors (see below), whose sum is σ = 25129280. Its totient is φ = 11214612.

The previous prime is 16821991. The next prime is 16822037. The reversal of 16821999 is 99912861.

It is not a de Polignac number, because 16821999 - 2³ = 16821991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16821991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 103759 + ... + 103920.

It is an arithmetic number, because the mean of its divisors is an integer number (2512928).

Almost surely, 2^16821999 is an apocalyptic number.

16821999 is a deficient number, since it is larger than the sum of its proper divisors (8307281).

16821999 is an equidigital number, since it uses as much as digits as its factorization.

16821999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 207691 (or 207682 counting only the distinct ones).

The product of its digits is 69984, while the sum is 45.

The square root of 16821999 is about 4101.4630316510. The cubic root of 16821999 is about 256.2275757494.

The spelling of 16821999 in words is "sixteen million, eight hundred twenty-one thousand, nine hundred ninety-nine".