128491309 has 2 divisors, whose sum is σ = 128491310. Its totient is φ = 128491308.

The previous prime is 128491301. The next prime is 128491313. The reversal of 128491309 is 903194821.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 117288900 + 11202409 = 10830^2 + 3347^2 .

It is a cyclic number.

It is not a de Polignac number, because 128491309 - 2³ = 128491301 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128491301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64245654 + 64245655.

It is an arithmetic number, because the mean of its divisors is an integer number (64245655).

Almost surely, 2^128491309 is an apocalyptic number.

It is an amenable number.

128491309 is a deficient number, since it is larger than the sum of its proper divisors (1).

128491309 is an equidigital number, since it uses as much as digits as its factorization.

128491309 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15552, while the sum is 37.

The square root of 128491309 is about 11335.4006986961. The cubic root of 128491309 is about 504.6123993770.

The spelling of 128491309 in words is "one hundred twenty-eight million, four hundred ninety-one thousand, three hundred nine".