209819923 has 2 divisors, whose sum is σ = 209819924. Its totient is φ = 209819922.

The previous prime is 209819921. The next prime is 209819963. The reversal of 209819923 is 329918902.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 209819923 - 2¹ = 209819921 is a prime.

Together with 209819921, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 209819923.

It is not a weakly prime, because it can be changed into another prime (209819921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 104909961 + 104909962.

It is an arithmetic number, because the mean of its divisors is an integer number (104909962).

Almost surely, 2^209819923 is an apocalyptic number.

209819923 is a deficient number, since it is larger than the sum of its proper divisors (1).

209819923 is an equidigital number, since it uses as much as digits as its factorization.

209819923 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 69984, while the sum is 43.

The square root of 209819923 is about 14485.1621668520. The cubic root of 209819923 is about 594.2222477004. Note that the first 4 decimals are identical.

The spelling of 209819923 in words is "two hundred nine million, eight hundred nineteen thousand, nine hundred twenty-three".