21008310823 has 2 divisors, whose sum is σ = 21008310824. Its totient is φ = 21008310822.

The previous prime is 21008310821. The next prime is 21008310863. The reversal of 21008310823 is 32801380012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21008310823 - 2¹ = 21008310821 is a prime.

Together with 21008310821, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21008310791 and 21008310800.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21008310821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504155411 + 10504155412.

It is an arithmetic number, because the mean of its divisors is an integer number (10504155412).

Almost surely, 2^21008310823 is an apocalyptic number.

21008310823 is a deficient number, since it is larger than the sum of its proper divisors (1).

21008310823 is an equidigital number, since it uses as much as digits as its factorization.

21008310823 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2304, while the sum is 28.

Adding to 21008310823 its reverse (32801380012), we get a palindrome (53809690835).

The spelling of 21008310823 in words is "twenty-one billion, eight million, three hundred ten thousand, eight hundred twenty-three".