28812821 has 2 divisors, whose sum is σ = 28812822. Its totient is φ = 28812820.

The previous prime is 28812799. The next prime is 28812877. The reversal of 28812821 is 12821882.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 26894596 + 1918225 = 5186^2 + 1385^2 .

It is a cyclic number.

It is not a de Polignac number, because 28812821 - 2¹⁸ = 28550677 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28812521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14406410 + 14406411.

It is an arithmetic number, because the mean of its divisors is an integer number (14406411).

Almost surely, 2^28812821 is an apocalyptic number.

It is an amenable number.

28812821 is a deficient number, since it is larger than the sum of its proper divisors (1).

28812821 is an equidigital number, since it uses as much as digits as its factorization.

28812821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4096, while the sum is 32.

The square root of 28812821 is about 5367.7575392337. The cubic root of 28812821 is about 306.5692516411.

The spelling of 28812821 in words is "twenty-eight million, eight hundred twelve thousand, eight hundred twenty-one".