128121609940 has 72 divisors (see below), whose sum is σ = 281649345768. Its totient is φ = 48952949760.

The previous prime is 128121609937. The next prime is 128121609953. The reversal of 128121609940 is 49906121821.

It can be written as a sum of positive squares in 4 ways, for example, as 1946044996 + 126175564944 = 44114^2 + 355212^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8043424 + ... + 8059336.

It is an arithmetic number, because the mean of its divisors is an integer number (3911796469).

Almost surely, 2^128121609940 is an apocalyptic number.

128121609940 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 128121609940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (140824672884).

128121609940 is an abundant number, since it is smaller than the sum of its proper divisors (153527735828).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

128121609940 is a wasteful number, since it uses less digits than its factorization.

128121609940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16729 (or 16704 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 43.

The spelling of 128121609940 in words is "one hundred twenty-eight billion, one hundred twenty-one million, six hundred nine thousand, nine hundred forty".