209999989 has 4 divisors (see below), whose sum is σ = 221052640. Its totient is φ = 198947340.

The previous prime is 209999987. The next prime is 210000017. The reversal of 209999989 is 989999902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 209999989 - 2¹ = 209999987 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 209999989.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209999981) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5526297 + ... + 5526334.

It is an arithmetic number, because the mean of its divisors is an integer number (55263160).

Almost surely, 2^209999989 is an apocalyptic number.

It is an amenable number.

209999989 is a deficient number, since it is larger than the sum of its proper divisors (11052651).

209999989 is a wasteful number, since it uses less digits than its factorization.

209999989 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11052650.

The product of its (nonzero) digits is 8503056, while the sum is 64.

The square root of 209999989 is about 14491.3763666534. The cubic root of 209999989 is about 594.3921848980.

The spelling of 209999989 in words is "two hundred nine million, nine hundred ninety-nine thousand, nine hundred eighty-nine".