71985209 has 2 divisors, whose sum is σ = 71985210. Its totient is φ = 71985208.

The previous prime is 71985169. The next prime is 71985211. The reversal of 71985209 is 90258917.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 42250000 + 29735209 = 6500^2 + 5453^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-71985209 is a prime.

Together with 71985211, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (71985229) 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, 35992604 + 35992605.

It is an arithmetic number, because the mean of its divisors is an integer number (35992605).

Almost surely, 2^71985209 is an apocalyptic number.

It is an amenable number.

71985209 is a deficient number, since it is larger than the sum of its proper divisors (1).

71985209 is an equidigital number, since it uses as much as digits as its factorization.

71985209 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 45360, while the sum is 41.

The square root of 71985209 is about 8484.4097614389. The cubic root of 71985209 is about 415.9882751411.

The spelling of 71985209 in words is "seventy-one million, nine hundred eighty-five thousand, two hundred nine".