21256043016449 has 2 divisors, whose sum is σ = 21256043016450. Its totient is φ = 21256043016448.

The previous prime is 21256043016433. The next prime is 21256043016487. The reversal of 21256043016449 is 94461034065212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18991641043600 + 2264401972849 = 4357940^2 + 1504793^2 .

It is a cyclic number.

It is not a de Polignac number, because 21256043016449 - 2⁴ = 21256043016433 is a prime.

It is not a weakly prime, because it can be changed into another prime (21256043016409) 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, 10628021508224 + 10628021508225.

It is an arithmetic number, because the mean of its divisors is an integer number (10628021508225).

Almost surely, 2^{21256043016449} is an apocalyptic number.

It is an amenable number.

21256043016449 is a deficient number, since it is larger than the sum of its proper divisors (1).

21256043016449 is an equidigital number, since it uses as much as digits as its factorization.

21256043016449 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1244160, while the sum is 47.

The spelling of 21256043016449 in words is "twenty-one trillion, two hundred fifty-six billion, forty-three million, sixteen thousand, four hundred forty-nine".