21456000991 has 2 divisors, whose sum is σ = 21456000992. Its totient is φ = 21456000990.

The previous prime is 21456000959. The next prime is 21456001013. The reversal of 21456000991 is 19900065412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21456000991 - 2⁵ = 21456000959 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21456000991.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21456000931) 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, 10728000495 + 10728000496.

It is an arithmetic number, because the mean of its divisors is an integer number (10728000496).

Almost surely, 2^21456000991 is an apocalyptic number.

21456000991 is the 84570-th hex number.

21456000991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21456000991 is an equidigital number, since it uses as much as digits as its factorization.

21456000991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 19440, while the sum is 37.

The spelling of 21456000991 in words is "twenty-one billion, four hundred fifty-six million, nine hundred ninety-one", and thus it is an aban number.