128991586 has 4 divisors (see below), whose sum is σ = 193487382. Its totient is φ = 64495792.

The previous prime is 128991557. The next prime is 128991607. The reversal of 128991586 is 685199821.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 685199821 = 67 ⋅10226863.

It can be written as a sum of positive squares in only one way, i.e., 128029225 + 962361 = 11315^2 + 981^2 .

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32247895 + ... + 32247898.

Almost surely, 2^128991586 is an apocalyptic number.

128991586 is a deficient number, since it is larger than the sum of its proper divisors (64495796).

128991586 is an equidigital number, since it uses as much as digits as its factorization.

128991586 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 64495795.

The product of its digits is 311040, while the sum is 49.

The square root of 128991586 is about 11357.4462798641. The cubic root of 128991586 is about 505.2664489411.

The spelling of 128991586 in words is "one hundred twenty-eight million, nine hundred ninety-one thousand, five hundred eighty-six".