128721165 has 8 divisors (see below), whose sum is σ = 205953888. Its totient is φ = 68651280.

The previous prime is 128721149. The next prime is 128721193. The reversal of 128721165 is 561127821.

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

It is not a de Polignac number, because 128721165 - 2⁴ = 128721149 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4290691 + ... + 4290720.

It is an arithmetic number, because the mean of its divisors is an integer number (25744236).

Almost surely, 2^128721165 is an apocalyptic number.

128721165 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

128721165 is a deficient number, since it is larger than the sum of its proper divisors (77232723).

128721165 is an equidigital number, since it uses as much as digits as its factorization.

128721165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8581419.

The product of its digits is 6720, while the sum is 33.

The square root of 128721165 is about 11345.5350248457. The cubic root of 128721165 is about 504.9131177527.

Adding to 128721165 its reverse (561127821), we get a palindrome (689848986).

The spelling of 128721165 in words is "one hundred twenty-eight million, seven hundred twenty-one thousand, one hundred sixty-five".