21003831281 has 2 divisors, whose sum is σ = 21003831282. Its totient is φ = 21003831280.

The previous prime is 21003831253. The next prime is 21003831287. The reversal of 21003831281 is 18213830012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20639632225 + 364199056 = 143665^2 + 19084^2 .

It is a cyclic number.

It is not a de Polignac number, because 21003831281 - 2³⁰ = 19930089457 is a prime.

It is a super-2 number, since 2×21003831281² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21003831287) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501915640 + 10501915641.

It is an arithmetic number, because the mean of its divisors is an integer number (10501915641).

Almost surely, 2^21003831281 is an apocalyptic number.

It is an amenable number.

21003831281 is a deficient number, since it is larger than the sum of its proper divisors (1).

21003831281 is an equidigital number, since it uses as much as digits as its factorization.

21003831281 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2304, while the sum is 29.

The spelling of 21003831281 in words is "twenty-one billion, three million, eight hundred thirty-one thousand, two hundred eighty-one".