2161971606891 has 8 divisors (see below), whose sum is σ = 3007960496640. Its totient is φ = 1378648560872.

The previous prime is 2161971606889. The next prime is 2161971606901. The reversal of 2161971606891 is 1986061791612.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 2161971606891 - 2¹ = 2161971606889 is a prime.

It is not an unprimeable number, because it can be changed into a prime (2161971606811) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15666460851 + ... + 15666460988.

It is an arithmetic number, because the mean of its divisors is an integer number (375995062080).

Almost surely, 2^{2161971606891} is an apocalyptic number.

2161971606891 is a deficient number, since it is larger than the sum of its proper divisors (845988889749).

2161971606891 is a wasteful number, since it uses less digits than its factorization.

2161971606891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31332921865.

The product of its (nonzero) digits is 1959552, while the sum is 57.

The spelling of 2161971606891 in words is "two trillion, one hundred sixty-one billion, nine hundred seventy-one million, six hundred six thousand, eight hundred ninety-one".