213681 has 8 divisors (see below), whose sum is σ = 306880. Its totient is φ = 131472.

The previous prime is 213659. The next prime is 213713. The reversal of 213681 is 186312.

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

It is not a de Polignac number, because 213681 - 2⁵ = 213649 is a prime.

It is a super-2 number, since 2×213681² = 91319139522, which contains 22 as substring.

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 7 ways as a sum of consecutive naturals, for example, 2701 + ... + 2778.

It is an arithmetic number, because the mean of its divisors is an integer number (38360).

2²¹³⁶⁸¹ is an apocalyptic number.

It is an amenable number.

213681 is a deficient number, since it is larger than the sum of its proper divisors (93199).

213681 is a wasteful number, since it uses less digits than its factorization.

213681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5495.

The product of its digits is 288, while the sum is 21.

The square root of 213681 is about 462.2564223459. The cubic root of 213681 is about 59.7845047342.

Adding to 213681 its reverse (186312), we get a palindrome (399993).

The spelling of 213681 in words is "two hundred thirteen thousand, six hundred eighty-one".