21491759999 has 2 divisors, whose sum is σ = 21491760000. Its totient is φ = 21491759998.

The previous prime is 21491759923. The next prime is 21491760007. The reversal of 21491759999 is 99995719412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21491759999 - 2¹⁶ = 21491694463 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21491759299) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10745879999 + 10745880000.

It is an arithmetic number, because the mean of its divisors is an integer number (10745880000).

Almost surely, 2^21491759999 is an apocalyptic number.

21491759999 is a deficient number, since it is larger than the sum of its proper divisors (1).

21491759999 is an equidigital number, since it uses as much as digits as its factorization.

21491759999 is an evil number, because the sum of its binary digits is even.

The product of its digits is 16533720, while the sum is 65.

The spelling of 21491759999 in words is "twenty-one billion, four hundred ninety-one million, seven hundred fifty-nine thousand, nine hundred ninety-nine".