21064443391 has 2 divisors, whose sum is σ = 21064443392. Its totient is φ = 21064443390.

The previous prime is 21064443373. The next prime is 21064443403. The reversal of 21064443391 is 19334446012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21064443391 - 2⁷ = 21064443263 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21064443391.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21064443991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10532221695 + 10532221696.

It is an arithmetic number, because the mean of its divisors is an integer number (10532221696).

Almost surely, 2^21064443391 is an apocalyptic number.

21064443391 is a deficient number, since it is larger than the sum of its proper divisors (1).

21064443391 is an equidigital number, since it uses as much as digits as its factorization.

21064443391 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 62208, while the sum is 37.

The spelling of 21064443391 in words is "twenty-one billion, sixty-four million, four hundred forty-three thousand, three hundred ninety-one".