213531 has 8 divisors (see below), whose sum is σ = 287760. Its totient is φ = 140832.

The previous prime is 213523. The next prime is 213533. The reversal of 213531 is 135312.

It is a happy number.

213531 is a nontrivial binomial coefficient, being equal to C(654, 2).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 213531 - 2³ = 213523 is a prime.

It is a super-2 number, since 2×213531² = 91190975922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 213531.

It is not an unprimeable number, because it can be changed into a prime (213533) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1 + ... + 653.

It is an arithmetic number, because the mean of its divisors is an integer number (35970).

2²¹³⁵³¹ is an apocalyptic number.

213531 is the 653-rd triangular number and also the 327-th hexagonal number.

213531 is a deficient number, since it is larger than the sum of its proper divisors (74229).

213531 is a wasteful number, since it uses less digits than its factorization.

213531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 765.

The product of its digits is 90, while the sum is 15.

The square root of 213531 is about 462.0941462516. The cubic root of 213531 is about 59.7705122643.

Adding to 213531 its reverse (135312), we get a palindrome (348843).

The spelling of 213531 in words is "two hundred thirteen thousand, five hundred thirty-one".