217681087 has 4 divisors (see below), whose sum is σ = 234425800. Its totient is φ = 200936376.

The previous prime is 217681069. The next prime is 217681091. The reversal of 217681087 is 780186712.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-217681087 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (217681187) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8372337 + ... + 8372362.

It is an arithmetic number, because the mean of its divisors is an integer number (58606450).

Almost surely, 2^217681087 is an apocalyptic number.

217681087 is a deficient number, since it is larger than the sum of its proper divisors (16744713).

217681087 is a wasteful number, since it uses less digits than its factorization.

217681087 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16744712.

The product of its (nonzero) digits is 37632, while the sum is 40.

The square root of 217681087 is about 14754.0193506719. The cubic root of 217681087 is about 601.5525412647.

The spelling of 217681087 in words is "two hundred seventeen million, six hundred eighty-one thousand, eighty-seven".