217680 has 40 divisors (see below), whose sum is σ = 675552. Its totient is φ = 57984.

The previous prime is 217667. The next prime is 217681. The reversal of 217680 is 86712.

217680 = T₇₅ + T₇₆ + ... + T₁₁₉.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an Ulam number.

It is a self number, because there is not a number n which added to its sum of digits gives 217680.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217681) by changing a digit.

217680 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 7 ways as a sum of consecutive naturals, for example, 214 + ... + 693.

2²¹⁷⁶⁸⁰ is an apocalyptic number.

217680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

217680 is an abundant number, since it is smaller than the sum of its proper divisors (457872).

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

217680 is a wasteful number, since it uses less digits than its factorization.

217680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 923 (or 917 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 217680 is about 466.5618930003. The cubic root of 217680 is about 60.1551539970.

The spelling of 217680 in words is "two hundred seventeen thousand, six hundred eighty".