21256043016487 has 2 divisors, whose sum is σ = 21256043016488. Its totient is φ = 21256043016486.

The previous prime is 21256043016449. The next prime is 21256043016541. The reversal of 21256043016487 is 78461034065212.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21256043016487 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21256043016487.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21256043016787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10628021508243 + 10628021508244.

It is an arithmetic number, because the mean of its divisors is an integer number (10628021508244).

Almost surely, 2^{21256043016487} is an apocalyptic number.

21256043016487 is a deficient number, since it is larger than the sum of its proper divisors (1).

21256043016487 is an equidigital number, since it uses as much as digits as its factorization.

21256043016487 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1935360, while the sum is 49.

The spelling of 21256043016487 in words is "twenty-one trillion, two hundred fifty-six billion, forty-three million, sixteen thousand, four hundred eighty-seven".