28217729 has 2 divisors, whose sum is σ = 28217730. Its totient is φ = 28217728.

The previous prime is 28217723. The next prime is 28217731. The reversal of 28217729 is 92771282.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 26832400 + 1385329 = 5180^2 + 1177^2 .

It is a cyclic number.

It is not a de Polignac number, because 28217729 - 2⁸ = 28217473 is a prime.

It is a Sophie Germain prime.

Together with 28217731, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 28217692 and 28217701.

It is not a weakly prime, because it can be changed into another prime (28217723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14108864 + 14108865.

It is an arithmetic number, because the mean of its divisors is an integer number (14108865).

Almost surely, 2^28217729 is an apocalyptic number.

It is an amenable number.

28217729 is a deficient number, since it is larger than the sum of its proper divisors (1).

28217729 is an equidigital number, since it uses as much as digits as its factorization.

28217729 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 28224, while the sum is 38.

The square root of 28217729 is about 5312.0362385812. The cubic root of 28217729 is about 304.4439532920.

The spelling of 28217729 in words is "twenty-eight million, two hundred seventeen thousand, seven hundred twenty-nine".