28027991 has 2 divisors, whose sum is σ = 28027992. Its totient is φ = 28027990.

The previous prime is 28027973. The next prime is 28028029. The reversal of 28027991 is 19972082.

It is an a-pointer prime, because the next prime (28028029) can be obtained adding 28027991 to its sum of digits (38).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 28027991 - 2¹⁰ = 28026967 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28027921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14013995 + 14013996.

It is an arithmetic number, because the mean of its divisors is an integer number (14013996).

Almost surely, 2^28027991 is an apocalyptic number.

28027991 is a deficient number, since it is larger than the sum of its proper divisors (1).

28027991 is an equidigital number, since it uses as much as digits as its factorization.

28027991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 28027991 is about 5294.1468623377. The cubic root of 28027991 is about 303.7600505856.

The spelling of 28027991 in words is "twenty-eight million, twenty-seven thousand, nine hundred ninety-one".