28881991 has 2 divisors, whose sum is σ = 28881992. Its totient is φ = 28881990.

The previous prime is 28881977. The next prime is 28882003. The reversal of 28881991 is 19918882.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 28881991 - 2²³ = 20493383 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28881961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14440995 + 14440996.

It is an arithmetic number, because the mean of its divisors is an integer number (14440996).

Almost surely, 2^28881991 is an apocalyptic number.

28881991 is a deficient number, since it is larger than the sum of its proper divisors (1).

28881991 is an equidigital number, since it uses as much as digits as its factorization.

28881991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 82944, while the sum is 46.

The square root of 28881991 is about 5374.1967771938. The cubic root of 28881991 is about 306.8143791915.

The spelling of 28881991 in words is "twenty-eight million, eight hundred eighty-one thousand, nine hundred ninety-one".