217864 has 16 divisors (see below), whose sum is σ = 413820. Its totient is φ = 107520.

The previous prime is 217859. The next prime is 217901. The reversal of 217864 is 468712.

217864 is nontrivially palindromic in base 15.

It can be written as a sum of positive squares in 2 ways, for example, as 209764 + 8100 = 458^2 + 90^2 .

It is an unprimeable 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, 784 + ... + 1024.

2²¹⁷⁸⁶⁴ is an apocalyptic number.

It is an amenable number.

217864 is a deficient number, since it is larger than the sum of its proper divisors (195956).

217864 is a wasteful number, since it uses less digits than its factorization.

217864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 360 (or 356 counting only the distinct ones).

The product of its digits is 2688, while the sum is 28.

The square root of 217864 is about 466.7590384770. The cubic root of 217864 is about 60.1720984891.

It can be divided in two parts, 217 and 864, that added together give a triangular number (1081 = T₄₆).

The spelling of 217864 in words is "two hundred seventeen thousand, eight hundred sixty-four".