21064643779 has 2 divisors, whose sum is σ = 21064643780. Its totient is φ = 21064643778.

The previous prime is 21064643773. The next prime is 21064643807. The reversal of 21064643779 is 97734646012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21064643779 - 2³³ = 12474709187 is a prime.

It is not a weakly prime, because it can be changed into another prime (21064643773) 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, 10532321889 + 10532321890.

It is an arithmetic number, because the mean of its divisors is an integer number (10532321890).

Almost surely, 2^21064643779 is an apocalyptic number.

21064643779 is a deficient number, since it is larger than the sum of its proper divisors (1).

21064643779 is an equidigital number, since it uses as much as digits as its factorization.

21064643779 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1524096, while the sum is 49.

The spelling of 21064643779 in words is "twenty-one billion, sixty-four million, six hundred forty-three thousand, seven hundred seventy-nine".