21280363821 has 20 divisors (see below), whose sum is σ = 32885367900. Its totient is φ = 13697703936.

The previous prime is 21280363813. The next prime is 21280363829. The reversal of 21280363821 is 12836308212.

21280363821 is a `hidden beast` number, since 2 + 12 + 8 + 0 + 3 + 638 + 2 + 1 = 666.

It is an interprime number because it is at equal distance from previous prime (21280363813) and next prime (21280363829).

It can be written as a sum of positive squares in 2 ways, for example, as 15998708196 + 5281655625 = 126486^2 + 72675^2 .

It is not a de Polignac number, because 21280363821 - 2³ = 21280363813 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21280363829) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 4527316 + ... + 4532013.

It is an arithmetic number, because the mean of its divisors is an integer number (1644268395).

Almost surely, 2^21280363821 is an apocalyptic number.

It is an amenable number.

21280363821 is a deficient number, since it is larger than the sum of its proper divisors (11605004079).

21280363821 is an equidigital number, since it uses as much as digits as its factorization.

21280363821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9059370 (or 9059361 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 36.

The spelling of 21280363821 in words is "twenty-one billion, two hundred eighty million, three hundred sixty-three thousand, eight hundred twenty-one".