217420287 has 32 divisors (see below), whose sum is σ = 354501120. Its totient is φ = 115758720.

The previous prime is 217420283. The next prime is 217420289. The reversal of 217420287 is 782024712.

It is not a de Polignac number, because 217420287 - 2² = 217420283 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217420283) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 19873 + ... + 28805.

It is an arithmetic number, because the mean of its divisors is an integer number (11078160).

Almost surely, 2^217420287 is an apocalyptic number.

217420287 is a deficient number, since it is larger than the sum of its proper divisors (137080833).

217420287 is a wasteful number, since it uses less digits than its factorization.

217420287 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9023.

The product of its (nonzero) digits is 12544, while the sum is 33.

The square root of 217420287 is about 14745.1784322876. The cubic root of 217420287 is about 601.3122086442.

Adding to 217420287 its reverse (782024712), we get a palindrome (999444999).

The spelling of 217420287 in words is "two hundred seventeen million, four hundred twenty thousand, two hundred eighty-seven".