28345781 has 2 divisors, whose sum is σ = 28345782. Its totient is φ = 28345780.

The previous prime is 28345763. The next prime is 28345813. The reversal of 28345781 is 18754382.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19140625 + 9205156 = 4375^2 + 3034^2 .

It is a cyclic number.

It is not a de Polignac number, because 28345781 - 2¹⁴ = 28329397 is a prime.

It is a super-2 number, since 2×28345781² = 1606966600999922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28345721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14172890 + 14172891.

It is an arithmetic number, because the mean of its divisors is an integer number (14172891).

Almost surely, 2^28345781 is an apocalyptic number.

It is an amenable number.

28345781 is a deficient number, since it is larger than the sum of its proper divisors (1).

28345781 is an equidigital number, since it uses as much as digits as its factorization.

28345781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 53760, while the sum is 38.

The square root of 28345781 is about 5324.0756005151. The cubic root of 28345781 is about 304.9037804520.

It can be divided in two parts, 283 and 45781, that added together give a palindrome (46064).

The spelling of 28345781 in words is "twenty-eight million, three hundred forty-five thousand, seven hundred eighty-one".