209951989 has 8 divisors (see below), whose sum is σ = 239402520. Its totient is φ = 182401536.

The previous prime is 209951947. The next prime is 209952019. The reversal of 209951989 is 989159902.

It can be written as a sum of positive squares in 4 ways, for example, as 1380625 + 208571364 = 1175^2 + 14442^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 209951989 - 2²⁷ = 75734261 is a prime.

It is a super-2 number, since 2×209951989² = 88159675370112242, 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 (209951689) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 474784 + ... + 475225.

It is an arithmetic number, because the mean of its divisors is an integer number (29925315).

Almost surely, 2^209951989 is an apocalyptic number.

It is an amenable number.

209951989 is a deficient number, since it is larger than the sum of its proper divisors (29450531).

209951989 is a wasteful number, since it uses less digits than its factorization.

209951989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 950039.

The product of its (nonzero) digits is 524880, while the sum is 52.

The square root of 209951989 is about 14489.7201146192. The cubic root of 209951989 is about 594.3468944212.

The spelling of 209951989 in words is "two hundred nine million, nine hundred fifty-one thousand, nine hundred eighty-nine".