9656211517991 has 4 divisors (see below), whose sum is σ = 9693784325712. Its totient is φ = 9618638710272.

The previous prime is 9656211517921. The next prime is 9656211518027. The reversal of 9656211517991 is 1997151126569.

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

It is a cyclic number.

It is not a de Polignac number, because 9656211517991 - 2²⁶ = 9656144409127 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 (9656211517921) 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, 18786403475 + ... + 18786403988.

It is an arithmetic number, because the mean of its divisors is an integer number (2423446081428).

Almost surely, 2^{9656211517991} is an apocalyptic number.

9656211517991 is a deficient number, since it is larger than the sum of its proper divisors (37572807721).

9656211517991 is a wasteful number, since it uses less digits than its factorization.

9656211517991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37572807720.

The product of its digits is 9185400, while the sum is 62.

The spelling of 9656211517991 in words is "nine trillion, six hundred fifty-six billion, two hundred eleven million, five hundred seventeen thousand, nine hundred ninety-one".