217640 has 16 divisors (see below), whose sum is σ = 489780. Its totient is φ = 87040.

The previous prime is 217619. The next prime is 217643. The reversal of 217640 is 46712.

217640 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 217156 + 484 = 466^2 + 22^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

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 217640.

It is not an unprimeable number, because it can be changed into a prime (217643) by changing a digit.

217640 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2681 + ... + 2760.

2²¹⁷⁶⁴⁰ is an apocalyptic number.

217640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

217640 is an abundant number, since it is smaller than the sum of its proper divisors (272140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

217640 is a wasteful number, since it uses less digits than its factorization.

217640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5452 (or 5448 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 217640 is about 466.5190242637. The cubic root of 217640 is about 60.1514691484.

The spelling of 217640 in words is "two hundred seventeen thousand, six hundred forty".