128029991 has 2 divisors, whose sum is σ = 128029992. Its totient is φ = 128029990.

The previous prime is 128029987. The next prime is 128030051. The reversal of 128029991 is 199920821.

It is a weak prime.

It is an emirp because it is prime and its reverse (199920821) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 128029991 - 2² = 128029987 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (128029901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64014995 + 64014996.

It is an arithmetic number, because the mean of its divisors is an integer number (64014996).

Almost surely, 2^128029991 is an apocalyptic number.

128029991 is a deficient number, since it is larger than the sum of its proper divisors (1).

128029991 is an equidigital number, since it uses as much as digits as its factorization.

128029991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23328, while the sum is 41.

The square root of 128029991 is about 11315.0338488225. The cubic root of 128029991 is about 504.0077776053.

The spelling of 128029991 in words is "one hundred twenty-eight million, twenty-nine thousand, nine hundred ninety-one".