1991081541601 has 8 divisors (see below), whose sum is σ = 1995469297344. Its totient is φ = 1986697831440.

The previous prime is 1991081541577. The next prime is 1991081541661. The reversal of 1991081541601 is 1061451801991.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1991081541601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991081541661) 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, 24930 + ... + 1995691.

It is an arithmetic number, because the mean of its divisors is an integer number (249433662168).

Almost surely, 2^{1991081541601} is an apocalyptic number.

It is an amenable number.

1991081541601 is a deficient number, since it is larger than the sum of its proper divisors (4387755743).

1991081541601 is a wasteful number, since it uses less digits than its factorization.

1991081541601 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2022791.

The product of its (nonzero) digits is 77760, while the sum is 46.

The spelling of 1991081541601 in words is "one trillion, nine hundred ninety-one billion, eighty-one million, five hundred forty-one thousand, six hundred one".