212309 has 4 divisors (see below), whose sum is σ = 219660. Its totient is φ = 204960.

The previous prime is 212297. The next prime is 212353. The reversal of 212309 is 903212.

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 34225 + 178084 = 185^2 + 422^2 .

It is a cyclic number.

It is not a de Polignac number, because 212309 - 2⁴ = 212293 is a prime.

It is a super-2 number, since 2×212309² = 90150222962, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a plaindrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (212369) 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 in 3 ways as a sum of consecutive naturals, for example, 3632 + ... + 3689.

It is an arithmetic number, because the mean of its divisors is an integer number (54915).

2²¹²³⁰⁹ is an apocalyptic number.

212309 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

212309 is a deficient number, since it is larger than the sum of its proper divisors (7351).

212309 is an equidigital number, since it uses as much as digits as its factorization.

212309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7350.

The product of its (nonzero) digits is 108, while the sum is 17.

The square root of 212309 is about 460.7700077045. The cubic root of 212309 is about 59.6562753908.

The spelling of 212309 in words is "two hundred twelve thousand, three hundred nine".