21641543849 has 2 divisors, whose sum is σ = 21641543850. Its totient is φ = 21641543848.

The previous prime is 21641543843. The next prime is 21641543863. The reversal of 21641543849 is 94834514612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20755588624 + 885955225 = 144068^2 + 29765^2 .

It is a cyclic number.

It is not a de Polignac number, because 21641543849 - 2⁸ = 21641543593 is a prime.

It is not a weakly prime, because it can be changed into another prime (21641543843) 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, 10820771924 + 10820771925.

It is an arithmetic number, because the mean of its divisors is an integer number (10820771925).

Almost surely, 2^21641543849 is an apocalyptic number.

It is an amenable number.

21641543849 is a deficient number, since it is larger than the sum of its proper divisors (1).

21641543849 is an equidigital number, since it uses as much as digits as its factorization.

21641543849 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 829440, while the sum is 47.

The spelling of 21641543849 in words is "twenty-one billion, six hundred forty-one million, five hundred forty-three thousand, eight hundred forty-nine".