215866 has 16 divisors (see below), whose sum is σ = 392256. Its totient is φ = 86976.

The previous prime is 215863. The next prime is 215893. The reversal of 215866 is 668512.

It is not an unprimeable number, because it can be changed into a prime (215863) 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, 216 + ... + 691.

It is an arithmetic number, because the mean of its divisors is an integer number (24516).

2²¹⁵⁸⁶⁶ is an apocalyptic number.

215866 is a deficient number, since it is larger than the sum of its proper divisors (176390).

215866 is a wasteful number, since it uses less digits than its factorization.

215866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 933.

The product of its digits is 2880, while the sum is 28.

The square root of 215866 is about 464.6138181329. The cubic root of 215866 is about 59.9875900260.

It can be divided in two parts, 215 and 866, that added together give a triangular number (1081 = T₄₆).

The spelling of 215866 in words is "two hundred fifteen thousand, eight hundred sixty-six".