128720550 has 144 divisors (see below), whose sum is σ = 377600832. Its totient is φ = 28929600.

The previous prime is 128720539. The next prime is 128720551. The reversal of 128720550 is 55027821.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128720551) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 609945 + ... + 610155.

It is an arithmetic number, because the mean of its divisors is an integer number (2622228).

Almost surely, 2^128720550 is an apocalyptic number.

128720550 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 128720550, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (188800416).

128720550 is an abundant number, since it is smaller than the sum of its proper divisors (248880282).

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

128720550 is a wasteful number, since it uses less digits than its factorization.

128720550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323 (or 311 counting only the distinct ones).

The product of its (nonzero) digits is 5600, while the sum is 30.

The square root of 128720550 is about 11345.5079216402. The cubic root of 128720550 is about 504.9123136320.

The spelling of 128720550 in words is "one hundred twenty-eight million, seven hundred twenty thousand, five hundred fifty".