28717681 has 2 divisors, whose sum is σ = 28717682. Its totient is φ = 28717680.

The previous prime is 28717657. The next prime is 28717691. The reversal of 28717681 is 18671782.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 22240656 + 6477025 = 4716^2 + 2545^2 .

It is a cyclic number.

It is not a de Polignac number, because 28717681 - 2⁵ = 28717649 is a prime.

It is a super-2 number, since 2×28717681² = 1649410404035522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (28717651) 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, 14358840 + 14358841.

It is an arithmetic number, because the mean of its divisors is an integer number (14358841).

Almost surely, 2^28717681 is an apocalyptic number.

It is an amenable number.

28717681 is a deficient number, since it is larger than the sum of its proper divisors (1).

28717681 is an equidigital number, since it uses as much as digits as its factorization.

28717681 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 37632, while the sum is 40.

The square root of 28717681 is about 5358.8880376436. Note that the first 3 decimals coincide. The cubic root of 28717681 is about 306.2314487722.

The spelling of 28717681 in words is "twenty-eight million, seven hundred seventeen thousand, six hundred eighty-one".