28208681 has 2 divisors, whose sum is σ = 28208682. Its totient is φ = 28208680.

The previous prime is 28208641. The next prime is 28208683. The reversal of 28208681 is 18680282.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 22992025 + 5216656 = 4795^2 + 2284^2 .

It is a cyclic number.

It is not a de Polignac number, because 28208681 - 2¹⁸ = 27946537 is a prime.

It is a super-2 number, since 2×28208681² = 1591459367519522, which contains 22 as substring.

It is a Sophie Germain prime.

Together with 28208683, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is equal to p_1753586 and since 28208681 and 1753586 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (28208683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14104340 + 14104341.

It is an arithmetic number, because the mean of its divisors is an integer number (14104341).

Almost surely, 2^28208681 is an apocalyptic number.

It is an amenable number.

28208681 is a deficient number, since it is larger than the sum of its proper divisors (1).

28208681 is an equidigital number, since it uses as much as digits as its factorization.

28208681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12288, while the sum is 35.

The square root of 28208681 is about 5311.1845194834. The cubic root of 28208681 is about 304.4114098821.

The spelling of 28208681 in words is "twenty-eight million, two hundred eight thousand, six hundred eighty-one".