891945209 has 2 divisors, whose sum is σ = 891945210. Its totient is φ = 891945208.

The previous prime is 891945191. The next prime is 891945211. The reversal of 891945209 is 902549198.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 872611600 + 19333609 = 29540^2 + 4397^2 .

It is a cyclic number.

It is not a de Polignac number, because 891945209 - 2⁸ = 891944953 is a prime.

Together with 891945211, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p_45618599 and since 891945209 and 45618599 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (891941209) 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 as a sum of consecutive naturals, namely, 445972604 + 445972605.

It is an arithmetic number, because the mean of its divisors is an integer number (445972605).

Almost surely, 2^891945209 is an apocalyptic number.

It is an amenable number.

891945209 is a deficient number, since it is larger than the sum of its proper divisors (1).

891945209 is an equidigital number, since it uses as much as digits as its factorization.

891945209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 233280, while the sum is 47.

The square root of 891945209 is about 29865.4517628647. The cubic root of 891945209 is about 962.6004470196.

The spelling of 891945209 in words is "eight hundred ninety-one million, nine hundred forty-five thousand, two hundred nine".