217979887688 has 8 divisors (see below), whose sum is σ = 408712289430. Its totient is φ = 108989943840.

The previous prime is 217979887663. The next prime is 217979887747. The reversal of 217979887688 is 886788979712.

It can be written as a sum of positive squares in only one way, i.e., 217978801924 + 1085764 = 466882^2 + 1042^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an unprimeable number.

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 as a sum of consecutive naturals, namely, 13623742973 + ... + 13623742988.

Almost surely, 2^217979887688 is an apocalyptic number.

It is an amenable number.

217979887688 is a deficient number, since it is larger than the sum of its proper divisors (190732401742).

217979887688 is a wasteful number, since it uses less digits than its factorization.

217979887688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27247485967 (or 27247485963 counting only the distinct ones).

The product of its digits is 1365590016, while the sum is 80.

The spelling of 217979887688 in words is "two hundred seventeen billion, nine hundred seventy-nine million, eight hundred eighty-seven thousand, six hundred eighty-eight".