213691 has 4 divisors (see below), whose sum is σ = 215992. Its totient is φ = 211392.

The previous prime is 213659. The next prime is 213713. The reversal of 213691 is 196312.

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

It is a cyclic number.

It is not a de Polignac number, because 213691 - 2⁵ = 213659 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (213611) 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, 1005 + ... + 1198.

It is an arithmetic number, because the mean of its divisors is an integer number (53998).

2²¹³⁶⁹¹ is an apocalyptic number.

213691 is a deficient number, since it is larger than the sum of its proper divisors (2301).

213691 is an equidigital number, since it uses as much as digits as its factorization.

213691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2300.

The product of its digits is 324, while the sum is 22.

The square root of 213691 is about 462.2672387267. The cubic root of 213691 is about 59.7854373327.

It can be divided in two parts, 2136 and 91, that multiplied together give a triangular number (194376 = T₆₂₃).

The spelling of 213691 in words is "two hundred thirteen thousand, six hundred ninety-one".