28776821 has 2 divisors, whose sum is σ = 28776822. Its totient is φ = 28776820.

The previous prime is 28776799. The next prime is 28776829. The reversal of 28776821 is 12867782.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18447025 + 10329796 = 4295^2 + 3214^2 .

It is a cyclic number.

It is not a de Polignac number, because 28776821 - 2⁶ = 28776757 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28776829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14388410 + 14388411.

It is an arithmetic number, because the mean of its divisors is an integer number (14388411).

Almost surely, 2^28776821 is an apocalyptic number.

It is an amenable number.

28776821 is a deficient number, since it is larger than the sum of its proper divisors (1).

28776821 is an equidigital number, since it uses as much as digits as its factorization.

28776821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 75264, while the sum is 41.

The square root of 28776821 is about 5364.4031354849. The cubic root of 28776821 is about 306.4415180794.

The spelling of 28776821 in words is "twenty-eight million, seven hundred seventy-six thousand, eight hundred twenty-one".