21251442481 has 2 divisors, whose sum is σ = 21251442482. Its totient is φ = 21251442480.

The previous prime is 21251442451. The next prime is 21251442539. The reversal of 21251442481 is 18424415212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13014246400 + 8237196081 = 114080^2 + 90759^2 .

It is a cyclic number.

It is not a de Polignac number, because 21251442481 - 2¹⁹ = 21250918193 is a prime.

It is a super-2 number, since 2×21251442481² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21251442451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10625721240 + 10625721241.

It is an arithmetic number, because the mean of its divisors is an integer number (10625721241).

Almost surely, 2^21251442481 is an apocalyptic number.

It is an amenable number.

21251442481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21251442481 is an equidigital number, since it uses as much as digits as its factorization.

21251442481 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 20480, while the sum is 34.

Adding to 21251442481 its reverse (18424415212), we get a palindrome (39675857693).

The spelling of 21251442481 in words is "twenty-one billion, two hundred fifty-one million, four hundred forty-two thousand, four hundred eighty-one".