213581 has 4 divisors (see below), whose sum is σ = 218592. Its totient is φ = 208572.

The previous prime is 213557. The next prime is 213589. The reversal of 213581 is 185312.

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 213581 - 2¹⁰ = 212557 is a prime.

It is a super-2 number, since 2×213581² = 91233687122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 213581.

It is not an unprimeable number, because it can be changed into a prime (213589) 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, 2441 + ... + 2526.

It is an arithmetic number, because the mean of its divisors is an integer number (54648).

2²¹³⁵⁸¹ is an apocalyptic number.

It is an amenable number.

213581 is a deficient number, since it is larger than the sum of its proper divisors (5011).

213581 is an equidigital number, since it uses as much as digits as its factorization.

213581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5010.

The product of its digits is 240, while the sum is 20.

The square root of 213581 is about 462.1482446142. The cubic root of 213581 is about 59.7751771488.

Adding to 213581 its reverse (185312), we get a palindrome (398893).

It can be divided in two parts, 213 and 581, that multiplied together give a triangular number (123753 = T₄₉₇).

The spelling of 213581 in words is "two hundred thirteen thousand, five hundred eighty-one".