28865821 has 2 divisors, whose sum is σ = 28865822. Its totient is φ = 28865820.

The previous prime is 28865803. The next prime is 28865843. The reversal of 28865821 is 12856882.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 27984100 + 881721 = 5290^2 + 939^2 .

It is a cyclic number.

It is not a de Polignac number, because 28865821 - 2¹³ = 28857629 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28865801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14432910 + 14432911.

It is an arithmetic number, because the mean of its divisors is an integer number (14432911).

Almost surely, 2^28865821 is an apocalyptic number.

It is an amenable number.

28865821 is a deficient number, since it is larger than the sum of its proper divisors (1).

28865821 is an equidigital number, since it uses as much as digits as its factorization.

28865821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 61440, while the sum is 40.

The square root of 28865821 is about 5372.6921557074. The cubic root of 28865821 is about 306.7571103481.

The spelling of 28865821 in words is "twenty-eight million, eight hundred sixty-five thousand, eight hundred twenty-one".