129538728 has 72 divisors (see below), whose sum is σ = 385653450. Its totient is φ = 39251520.

The previous prime is 129538709. The next prime is 129538733. The reversal of 129538728 is 827835921.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 121484484 + 8054244 = 11022^2 + 2838^2 .

It is a tau number, because it is divible by the number of its divisors (72).

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 1278 + ... + 16146.

Almost surely, 2^129538728 is an apocalyptic number.

129538728 is a gapful number since it is divisible by the number (18) 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 129538728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (192826725).

129538728 is an abundant number, since it is smaller than the sum of its proper divisors (256114722).

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

129538728 is a wasteful number, since it uses less digits than its factorization.

129538728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14903 (or 14885 counting only the distinct ones).

The product of its digits is 241920, while the sum is 45.

The square root of 129538728 is about 11381.5081601693. The cubic root of 129538728 is about 505.9798353653.

The spelling of 129538728 in words is "one hundred twenty-nine million, five hundred thirty-eight thousand, seven hundred twenty-eight".