217381 has 4 divisors (see below), whose sum is σ = 218764. Its totient is φ = 216000.

The previous prime is 217369. The next prime is 217387. The reversal of 217381 is 183712.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1156 + 216225 = 34^2 + 465^2 .

It is a 3-Lehmer number, since φ(217381) divides (217381-1)³.

It is a cyclic number.

It is not a de Polignac number, because 217381 - 2⁷ = 217253 is a prime.

It is a super-2 number, since 2×217381² = 94508998322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217387) 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, 420 + ... + 781.

It is an arithmetic number, because the mean of its divisors is an integer number (54691).

2²¹⁷³⁸¹ is an apocalyptic number.

It is an amenable number.

217381 is a deficient number, since it is larger than the sum of its proper divisors (1383).

217381 is a wasteful number, since it uses less digits than its factorization.

217381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1382.

The product of its digits is 336, while the sum is 22.

The square root of 217381 is about 466.2413538072. The cubic root of 217381 is about 60.1275988204.

The spelling of 217381 in words is "two hundred seventeen thousand, three hundred eighty-one".