128721331 has 8 divisors (see below), whose sum is σ = 140690304. Its totient is φ = 117240960.

The previous prime is 128721301. The next prime is 128721347. The reversal of 128721331 is 133127821.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 128721331 - 2⁹ = 128720819 is a prime.

It is a super-2 number, since 2×128721331² = 33138362108823122, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 128721331.

It is not an unprimeable number, because it can be changed into a prime (128721301) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 121600 + ... + 122653.

It is an arithmetic number, because the mean of its divisors is an integer number (17586288).

Almost surely, 2^128721331 is an apocalyptic number.

128721331 is a deficient number, since it is larger than the sum of its proper divisors (11968973).

128721331 is a wasteful number, since it uses less digits than its factorization.

128721331 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244301.

The product of its digits is 2016, while the sum is 28.

The square root of 128721331 is about 11345.5423404966. The cubic root of 128721331 is about 504.9133347995.

The spelling of 128721331 in words is "one hundred twenty-eight million, seven hundred twenty-one thousand, three hundred thirty-one".