128506521991 has 8 divisors (see below), whose sum is σ = 136530695520. Its totient is φ = 120721876128.

The previous prime is 128506521977. The next prime is 128506522051. The reversal of 128506521991 is 199125605821.

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 128506521991 - 2¹¹ = 128506519943 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 (128506521911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 59880811 + ... + 59882956.

It is an arithmetic number, because the mean of its divisors is an integer number (17066336940).

Almost surely, 2^128506521991 is an apocalyptic number.

128506521991 is a deficient number, since it is larger than the sum of its proper divisors (8024173529).

128506521991 is a wasteful number, since it uses less digits than its factorization.

128506521991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 119763833.

The product of its (nonzero) digits is 388800, while the sum is 49.

The spelling of 128506521991 in words is "one hundred twenty-eight billion, five hundred six million, five hundred twenty-one thousand, nine hundred ninety-one".