28989991 has 16 divisors (see below), whose sum is σ = 31933440. Its totient is φ = 26213760.

The previous prime is 28989977. The next prime is 28989997. The reversal of 28989991 is 19998982.

It is a cyclic number.

It is not a de Polignac number, because 28989991 - 2¹⁵ = 28957223 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28989997) 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, 48591 + ... + 49183.

It is an arithmetic number, because the mean of its divisors is an integer number (1995840).

Almost surely, 2^28989991 is an apocalyptic number.

28989991 is a deficient number, since it is larger than the sum of its proper divisors (2943449).

28989991 is a wasteful number, since it uses less digits than its factorization.

28989991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 726.

The product of its digits is 839808, while the sum is 55.

The square root of 28989991 is about 5384.2354146155. The cubic root of 28989991 is about 307.1963327323.

The spelling of 28989991 in words is "twenty-eight million, nine hundred eighty-nine thousand, nine hundred ninety-one".