21256472689 has 2 divisors, whose sum is σ = 21256472690. Its totient is φ = 21256472688.

The previous prime is 21256472681. The next prime is 21256472711. The reversal of 21256472689 is 98627465212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19053109089 + 2203363600 = 138033^2 + 46940^2 .

It is a cyclic number.

It is not a de Polignac number, because 21256472689 - 2³ = 21256472681 is a prime.

It is not a weakly prime, because it can be changed into another prime (21256472681) 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 as a sum of consecutive naturals, namely, 10628236344 + 10628236345.

It is an arithmetic number, because the mean of its divisors is an integer number (10628236345).

Almost surely, 2^21256472689 is an apocalyptic number.

It is an amenable number.

21256472689 is a deficient number, since it is larger than the sum of its proper divisors (1).

21256472689 is an equidigital number, since it uses as much as digits as its factorization.

21256472689 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2903040, while the sum is 52.

The spelling of 21256472689 in words is "twenty-one billion, two hundred fifty-six million, four hundred seventy-two thousand, six hundred eighty-nine".