128821121561 has 16 divisors (see below), whose sum is σ = 149026739328. Its totient is φ = 110052384000.

The previous prime is 128821121537. The next prime is 128821121587. The reversal of 128821121561 is 165121128821.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-128821121561 is a prime.

It is not an unprimeable number, because it can be changed into a prime (128821121461) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 405365 + ... + 649586.

It is an arithmetic number, because the mean of its divisors is an integer number (9314171208).

Almost surely, 2^128821121561 is an apocalyptic number.

128821121561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

128821121561 is a deficient number, since it is larger than the sum of its proper divisors (20205617767).

128821121561 is a wasteful number, since it uses less digits than its factorization.

128821121561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1055632.

The product of its digits is 15360, while the sum is 38.

The spelling of 128821121561 in words is "one hundred twenty-eight billion, eight hundred twenty-one million, one hundred twenty-one thousand, five hundred sixty-one".