28240391 has 2 divisors, whose sum is σ = 28240392. Its totient is φ = 28240390.

The previous prime is 28240357. The next prime is 28240393. The reversal of 28240391 is 19304282.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28240391 is a prime.

Together with 28240393, 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 (28240393) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14120195 + 14120196.

It is an arithmetic number, because the mean of its divisors is an integer number (14120196).

Almost surely, 2^28240391 is an apocalyptic number.

28240391 is a deficient number, since it is larger than the sum of its proper divisors (1).

28240391 is an equidigital number, since it uses as much as digits as its factorization.

28240391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 28240391 is about 5314.1688908050. The cubic root of 28240391 is about 304.5254323593.

The spelling of 28240391 in words is "twenty-eight million, two hundred forty thousand, three hundred ninety-one".