128640491 has 16 divisors (see below), whose sum is σ = 153144000. Its totient is φ = 105721728.

The previous prime is 128640461. The next prime is 128640497. The reversal of 128640491 is 194046821.

It is a happy number.

It is not a de Polignac number, because 128640491 - 2¹⁴ = 128624107 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (128640497) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28121 + ... + 32373.

It is an arithmetic number, because the mean of its divisors is an integer number (9571500).

Almost surely, 2^128640491 is an apocalyptic number.

128640491 is a deficient number, since it is larger than the sum of its proper divisors (24503509).

128640491 is a wasteful number, since it uses less digits than its factorization.

128640491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4438.

The product of its (nonzero) digits is 13824, while the sum is 35.

The square root of 128640491 is about 11341.9791482792. The cubic root of 128640491 is about 504.8076135452.

The spelling of 128640491 in words is "one hundred twenty-eight million, six hundred forty thousand, four hundred ninety-one".