217938681 has 12 divisors (see below), whose sum is σ = 326459952. Its totient is φ = 145292292.

The previous prime is 217938673. The next prime is 217938701. The reversal of 217938681 is 186839712.

It is not a de Polignac number, because 217938681 - 2³ = 217938673 is a prime.

It is a super-2 number, since 2×217938681² = 94994537352039522, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (217938481) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 448191 + ... + 448676.

It is an arithmetic number, because the mean of its divisors is an integer number (27204996).

Almost surely, 2^217938681 is an apocalyptic number.

It is an amenable number.

217938681 is a deficient number, since it is larger than the sum of its proper divisors (108521271).

217938681 is an frugal number, since it uses more digits than its factorization.

217938681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 896882 (or 896870 counting only the distinct ones).

The product of its digits is 145152, while the sum is 45.

The square root of 217938681 is about 14762.7463908312. The cubic root of 217938681 is about 601.7897311294.

The spelling of 217938681 in words is "two hundred seventeen million, nine hundred thirty-eight thousand, six hundred eighty-one".