128744021 has 30 divisors (see below), whose sum is σ = 159068790. Its totient is φ = 104068944.

The previous prime is 128744003. The next prime is 128744027. The reversal of 128744021 is 120447821.

It can be written as a sum of positive squares in only one way, i.e., 110986225 + 17757796 = 10535^2 + 4214^2 .

It is not a de Polignac number, because 128744021 - 2¹⁴ = 128727637 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (128744027) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 2994026 + ... + 2994068.

It is an arithmetic number, because the mean of its divisors is an integer number (5302293).

Almost surely, 2^128744021 is an apocalyptic number.

It is an amenable number.

128744021 is a deficient number, since it is larger than the sum of its proper divisors (30324769).

128744021 is an frugal number, since it uses more digits than its factorization.

128744021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143 (or 79 counting only the distinct ones).

The product of its (nonzero) digits is 3584, while the sum is 29.

The square root of 128744021 is about 11346.5422486324. The cubic root of 128744021 is about 504.9430004614.

Multiplying 128744021 by its sum of digits (29), we get a square (3733576609 = 61103²).

128744021 divided by its sum of digits (29) gives a square (4439449 = 2107²).

The spelling of 128744021 in words is "one hundred twenty-eight million, seven hundred forty-four thousand, twenty-one".