28756781 has 2 divisors, whose sum is σ = 28756782. Its totient is φ = 28756780.

The previous prime is 28756771. The next prime is 28756787. The reversal of 28756781 is 18765782.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 25300900 + 3455881 = 5030^2 + 1859^2 .

It is a cyclic number.

It is not a de Polignac number, because 28756781 - 2¹⁸ = 28494637 is a prime.

It is a super-2 number, since 2×28756781² = 1653904906963922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28756787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14378390 + 14378391.

It is an arithmetic number, because the mean of its divisors is an integer number (14378391).

Almost surely, 2^28756781 is an apocalyptic number.

It is an amenable number.

28756781 is a deficient number, since it is larger than the sum of its proper divisors (1).

28756781 is an equidigital number, since it uses as much as digits as its factorization.

28756781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 188160, while the sum is 44.

The square root of 28756781 is about 5362.5349416111. The cubic root of 28756781 is about 306.3703669017.

Subtracting from 28756781 its reverse (18765782), we obtain a palindrome (9990999).

The spelling of 28756781 in words is "twenty-eight million, seven hundred fifty-six thousand, seven hundred eighty-one".