28978991 has 2 divisors, whose sum is σ = 28978992. Its totient is φ = 28978990.

The previous prime is 28978981. The next prime is 28978993. The reversal of 28978991 is 19987982.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 28978991 - 2⁶ = 28978927 is a prime.

It is a Sophie Germain prime.

Together with 28978993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28978993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14489495 + 14489496.

It is an arithmetic number, because the mean of its divisors is an integer number (14489496).

Almost surely, 2^28978991 is an apocalyptic number.

28978991 is a deficient number, since it is larger than the sum of its proper divisors (1).

28978991 is an equidigital number, since it uses as much as digits as its factorization.

28978991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 653184, while the sum is 53.

The square root of 28978991 is about 5383.2138170428. The cubic root of 28978991 is about 307.1574734912.

The spelling of 28978991 in words is "twenty-eight million, nine hundred seventy-eight thousand, nine hundred ninety-one".