9721666518 has 16 divisors (see below), whose sum is σ = 19512529776. Its totient is φ = 3229022720.

The previous prime is 9721666499. The next prime is 9721666523. The reversal of 9721666518 is 8156661279.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2881371 + ... + 2884742.

It is an arithmetic number, because the mean of its divisors is an integer number (1219533111).

Almost surely, 2^9721666518 is an apocalyptic number.

9721666518 is an abundant number, since it is smaller than the sum of its proper divisors (9790863258).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

9721666518 is a wasteful number, since it uses less digits than its factorization.

9721666518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5766399.

The product of its digits is 1088640, while the sum is 51.

The square root of 9721666518 is about 98598.5117433321. The cubic root of 9721666518 is about 2134.2579433521.

The spelling of 9721666518 in words is "nine billion, seven hundred twenty-one million, six hundred sixty-six thousand, five hundred eighteen".