209978243 has 2 divisors, whose sum is σ = 209978244. Its totient is φ = 209978242.

The previous prime is 209978213. The next prime is 209978267. The reversal of 209978243 is 342879902.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 209978243 - 2¹⁰ = 209977219 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 209978194 and 209978203.

It is not a weakly prime, because it can be changed into another prime (209978213) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104989121 + 104989122.

It is an arithmetic number, because the mean of its divisors is an integer number (104989122).

Almost surely, 2^209978243 is an apocalyptic number.

209978243 is a deficient number, since it is larger than the sum of its proper divisors (1).

209978243 is an equidigital number, since it uses as much as digits as its factorization.

209978243 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 217728, while the sum is 44.

The square root of 209978243 is about 14490.6260389260. The cubic root of 209978243 is about 594.3716672801.

The spelling of 209978243 in words is "two hundred nine million, nine hundred seventy-eight thousand, two hundred forty-three".