128391994 has 4 divisors (see below), whose sum is σ = 192587994. Its totient is φ = 64195996.

The previous prime is 128391971. The next prime is 128391997. The reversal of 128391994 is 499193821.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 98743969 + 29648025 = 9937^2 + 5445^2 .

It is not an unprimeable number, because it can be changed into a prime (128391997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32097997 + ... + 32098000.

Almost surely, 2^128391994 is an apocalyptic number.

128391994 is a deficient number, since it is larger than the sum of its proper divisors (64196000).

128391994 is an equidigital number, since it uses as much as digits as its factorization.

128391994 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64195999.

The product of its digits is 139968, while the sum is 46.

The square root of 128391994 is about 11331.0191068588. The cubic root of 128391994 is about 504.4823555674.

The spelling of 128391994 in words is "one hundred twenty-eight million, three hundred ninety-one thousand, nine hundred ninety-four".