28297997821 has 2 divisors, whose sum is σ = 28297997822. Its totient is φ = 28297997820.

The previous prime is 28297997801. The next prime is 28297997851. The reversal of 28297997821 is 12879979282.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17850296025 + 10447701796 = 133605^2 + 102214^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28297997821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28297997801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14148998910 + 14148998911.

It is an arithmetic number, because the mean of its divisors is an integer number (14148998911).

Almost surely, 2^28297997821 is an apocalyptic number.

It is an amenable number.

28297997821 is a deficient number, since it is larger than the sum of its proper divisors (1).

28297997821 is an equidigital number, since it uses as much as digits as its factorization.

28297997821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18289152, while the sum is 64.

The spelling of 28297997821 in words is "twenty-eight billion, two hundred ninety-seven million, nine hundred ninety-seven thousand, eight hundred twenty-one".