28728581821 has 2 divisors, whose sum is σ = 28728581822. Its totient is φ = 28728581820.

The previous prime is 28728581767. The next prime is 28728581863. The reversal of 28728581821 is 12818582782.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 26835026596 + 1893555225 = 163814^2 + 43515^2 .

It is a cyclic number.

It is not a de Polignac number, because 28728581821 - 2⁹ = 28728581309 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28728584821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14364290910 + 14364290911.

It is an arithmetic number, because the mean of its divisors is an integer number (14364290911).

Almost surely, 2^28728581821 is an apocalyptic number.

It is an amenable number.

28728581821 is a deficient number, since it is larger than the sum of its proper divisors (1).

28728581821 is an equidigital number, since it uses as much as digits as its factorization.

28728581821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1146880, while the sum is 52.

The spelling of 28728581821 in words is "twenty-eight billion, seven hundred twenty-eight million, five hundred eighty-one thousand, eight hundred twenty-one".