209990999 has 4 divisors (see below), whose sum is σ = 210046560. Its totient is φ = 209935440.

The previous prime is 209990981. The next prime is 209991029. The reversal of 209990999 is 999099902.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 999099902 = 2 ⋅499549951.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-209990999 is a prime.

It is a super-2 number, since 2×209990999² = 88192439322036002, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209990699) 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 3 ways as a sum of consecutive naturals, for example, 21662 + ... + 29819.

It is an arithmetic number, because the mean of its divisors is an integer number (52511640).

Almost surely, 2^209990999 is an apocalyptic number.

209990999 is a deficient number, since it is larger than the sum of its proper divisors (55561).

209990999 is an equidigital number, since it uses as much as digits as its factorization.

209990999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55560.

The product of its (nonzero) digits is 1062882, while the sum is 56.

The square root of 209990999 is about 14491.0661788565. The cubic root of 209990999 is about 594.3837028944.

The spelling of 209990999 in words is "two hundred nine million, nine hundred ninety thousand, nine hundred ninety-nine".