217919979 has 24 divisors (see below), whose sum is σ = 320545472. Its totient is φ = 142631280.

The previous prime is 217919951. The next prime is 217919983. The reversal of 217919979 is 979919712.

It is not a de Polignac number, because 217919979 - 2¹⁹ = 217395691 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (217919929) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 315024 + ... + 315714.

Almost surely, 2^217919979 is an apocalyptic number.

217919979 is a deficient number, since it is larger than the sum of its proper divisors (102625493).

217919979 is a wasteful number, since it uses less digits than its factorization.

217919979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1287 (or 1284 counting only the distinct ones).

The product of its digits is 642978, while the sum is 54.

The square root of 217919979 is about 14762.1129585165. The cubic root of 217919979 is about 601.7725168171.

The spelling of 217919979 in words is "two hundred seventeen million, nine hundred nineteen thousand, nine hundred seventy-nine".