128718817821 has 64 divisors (see below), whose sum is σ = 211651319040. Its totient is φ = 76661406720.

The previous prime is 128718817811. The next prime is 128718817867.

128718817821 is nontrivially palindromic in base 10.

It is not a de Polignac number, because 128718817821 - 2¹⁰ = 128718816797 is a prime.

It is a super-2 number, since 2×128718817821² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128718817811) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 5994921 + ... + 6016353.

It is an arithmetic number, because the mean of its divisors is an integer number (3307051860).

Almost surely, 2^128718817821 is an apocalyptic number.

128718817821 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

128718817821 is a deficient number, since it is larger than the sum of its proper divisors (82932501219).

128718817821 is a wasteful number, since it uses less digits than its factorization.

128718817821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21803 (or 21797 counting only the distinct ones).

The product of its digits is 802816, while the sum is 54.

The spelling of 128718817821 in words is "one hundred twenty-eight billion, seven hundred eighteen million, eight hundred seventeen thousand, eight hundred twenty-one".