215689 has 2 divisors, whose sum is σ = 215690. Its totient is φ = 215688.

The previous prime is 215687. The next prime is 215693. The reversal of 215689 is 986512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 144400 + 71289 = 380^2 + 267^2 .

It is a cyclic number.

It is not a de Polignac number, because 215689 - 2¹ = 215687 is a prime.

Together with 215687, it forms a pair of twin primes.

It is an Ulam number.

It is a plaindrome in base 7.

It is a self number, because there is not a number n which added to its sum of digits gives 215689.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (215681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 107844 + 107845.

It is an arithmetic number, because the mean of its divisors is an integer number (107845).

2²¹⁵⁶⁸⁹ is an apocalyptic number.

It is an amenable number.

215689 is a deficient number, since it is larger than the sum of its proper divisors (1).

215689 is an equidigital number, since it uses as much as digits as its factorization.

215689 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 31.

The square root of 215689 is about 464.4232982959. The cubic root of 215689 is about 59.9711898722.

The spelling of 215689 in words is "two hundred fifteen thousand, six hundred eighty-nine".