217661971 has 4 divisors (see below), whose sum is σ = 217857952. Its totient is φ = 217465992.

The previous prime is 217661963. The next prime is 217661987. The reversal of 217661971 is 179166712.

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

It is a cyclic number.

It is not a de Polignac number, because 217661971 - 2³ = 217661963 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (217661921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 96315 + ... + 98548.

It is an arithmetic number, because the mean of its divisors is an integer number (54464488).

Almost surely, 2^217661971 is an apocalyptic number.

217661971 is a deficient number, since it is larger than the sum of its proper divisors (195981).

217661971 is a wasteful number, since it uses less digits than its factorization.

217661971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 195980.

The product of its digits is 31752, while the sum is 40.

The square root of 217661971 is about 14753.3715129797. The cubic root of 217661971 is about 601.5349319949.

The spelling of 217661971 in words is "two hundred seventeen million, six hundred sixty-one thousand, nine hundred seventy-one".