64540049201991 has 12 divisors (see below), whose sum is σ = 101699471469960. Its totient is φ = 39115181334480.

The previous prime is 64540049201987. The next prime is 64540049202059. The reversal of 64540049201991 is 19910294004546.

64540049201991 is a `hidden beast` number, since 6 + 4 + 5 + 400 + 49 + 2 + 0 + 199 + 1 = 666.

It is not a de Polignac number, because 64540049201991 - 2² = 64540049201987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64540049201791) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 325959844356 + ... + 325959844553.

It is an arithmetic number, because the mean of its divisors is an integer number (8474955955830).

Almost surely, 2^{64540049201991} is an apocalyptic number.

64540049201991 is a deficient number, since it is larger than the sum of its proper divisors (37159422267969).

64540049201991 is a wasteful number, since it uses less digits than its factorization.

64540049201991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 651919688926 (or 651919688923 counting only the distinct ones).

The product of its (nonzero) digits is 2799360, while the sum is 54.

The spelling of 64540049201991 in words is "sixty-four trillion, five hundred forty billion, forty-nine million, two hundred one thousand, nine hundred ninety-one".