217980655 has 4 divisors (see below), whose sum is σ = 261576792. Its totient is φ = 174384520.

The previous prime is 217980649. The next prime is 217980661. The reversal of 217980655 is 556089712.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (217980649) and next prime (217980661).

It is a de Polignac number, because none of the positive numbers 2^k-217980655 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21798061 + ... + 21798070.

It is an arithmetic number, because the mean of its divisors is an integer number (65394198).

Almost surely, 2^217980655 is an apocalyptic number.

217980655 is a deficient number, since it is larger than the sum of its proper divisors (43596137).

217980655 is an equidigital number, since it uses as much as digits as its factorization.

217980655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43596136.

The product of its (nonzero) digits is 151200, while the sum is 43.

The square root of 217980655 is about 14764.1679413369. The cubic root of 217980655 is about 601.8283626389.

The spelling of 217980655 in words is "two hundred seventeen million, nine hundred eighty thousand, six hundred fifty-five".