213509 has 4 divisors (see below), whose sum is σ = 222816. Its totient is φ = 204204.

The previous prime is 213491. The next prime is 213523. The reversal of 213509 is 905312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 213509 - 2⁸ = 213253 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 (213539) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4619 + ... + 4664.

It is an arithmetic number, because the mean of its divisors is an integer number (55704).

2²¹³⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

213509 is a deficient number, since it is larger than the sum of its proper divisors (9307).

213509 is an equidigital number, since it uses as much as digits as its factorization.

213509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9306.

The product of its (nonzero) digits is 270, while the sum is 20.

The square root of 213509 is about 462.0703409655. The cubic root of 213509 is about 59.7684594844.

The spelling of 213509 in words is "two hundred thirteen thousand, five hundred nine".