128321509 has 2 divisors, whose sum is σ = 128321510. Its totient is φ = 128321508.

The previous prime is 128321507. The next prime is 128321551. The reversal of 128321509 is 905123821.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 109788484 + 18533025 = 10478^2 + 4305^2 .

It is a cyclic number.

It is not a de Polignac number, because 128321509 - 2¹ = 128321507 is a prime.

Together with 128321507, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128321507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64160754 + 64160755.

It is an arithmetic number, because the mean of its divisors is an integer number (64160755).

Almost surely, 2^128321509 is an apocalyptic number.

It is an amenable number.

128321509 is a deficient number, since it is larger than the sum of its proper divisors (1).

128321509 is an equidigital number, since it uses as much as digits as its factorization.

128321509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 128321509 is about 11327.9084124122. The cubic root of 128321509 is about 504.3900212852.

It can be divided in two parts, 12832 and 1509, that added together give a palindrome (14341).

The spelling of 128321509 in words is "one hundred twenty-eight million, three hundred twenty-one thousand, five hundred nine".