215905 has 8 divisors (see below), whose sum is σ = 268200. Its totient is φ = 166656.

The previous prime is 215899. The next prime is 215909. The reversal of 215905 is 509512.

215905 is digitally balanced in base 2, 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 4 ways, for example, as 7056 + 208849 = 84^2 + 457^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 215905 - 2⁹ = 215393 is a prime.

It is a super-2 number, since 2×215905² = 93229938050, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (215909) 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, 600 + ... + 889.

It is an arithmetic number, because the mean of its divisors is an integer number (33525).

2²¹⁵⁹⁰⁵ is an apocalyptic number.

It is an amenable number.

215905 is a deficient number, since it is larger than the sum of its proper divisors (52295).

215905 is a wasteful number, since it uses less digits than its factorization.

215905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1523.

The product of its (nonzero) digits is 450, while the sum is 22.

The square root of 215905 is about 464.6557865775. The cubic root of 215905 is about 59.9912024138.

The spelling of 215905 in words is "two hundred fifteen thousand, nine hundred five".