212705309 has 4 divisors (see below), whose sum is σ = 225217404. Its totient is φ = 200193216.

The previous prime is 212705303. The next prime is 212705321. The reversal of 212705309 is 903507212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 76912900 + 135792409 = 8770^2 + 11653^2 .

It is a cyclic number.

It is not a de Polignac number, because 212705309 - 2²⁰ = 211656733 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (212705303) 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 in 3 ways as a sum of consecutive naturals, for example, 6256022 + ... + 6256055.

It is an arithmetic number, because the mean of its divisors is an integer number (56304351).

Almost surely, 2^212705309 is an apocalyptic number.

It is an amenable number.

212705309 is a deficient number, since it is larger than the sum of its proper divisors (12512095).

212705309 is a wasteful number, since it uses less digits than its factorization.

212705309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12512094.

The product of its (nonzero) digits is 3780, while the sum is 29.

The square root of 212705309 is about 14584.4200776034. The cubic root of 212705309 is about 596.9337167239.

The spelling of 212705309 in words is "two hundred twelve million, seven hundred five thousand, three hundred nine".