9721698727666 has 4 divisors (see below), whose sum is σ = 14582548091502. Its totient is φ = 4860849363832.

The previous prime is 9721698727619. The next prime is 9721698727667. The reversal of 9721698727666 is 6667278961279.

9721698727666 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It can be written as a sum of positive squares in only one way, i.e., 7072828551441 + 2648870176225 = 2659479^2 + 1627535^2 .

It is a super-2 number, since 2×9721698727666² (a number of 27 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 9721698727592 and 9721698727601.

It is not an unprimeable number, because it can be changed into a prime (9721698727667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2430424681915 + ... + 2430424681918.

Almost surely, 2^{9721698727666} is an apocalyptic number.

9721698727666 is a deficient number, since it is larger than the sum of its proper divisors (4860849363836).

9721698727666 is a wasteful number, since it uses less digits than its factorization.

9721698727666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4860849363835.

The product of its digits is 1152216576, while the sum is 76.

The spelling of 9721698727666 in words is "nine trillion, seven hundred twenty-one billion, six hundred ninety-eight million, seven hundred twenty-seven thousand, six hundred sixty-six".