21008211823 has 2 divisors, whose sum is σ = 21008211824. Its totient is φ = 21008211822.

The previous prime is 21008211817. The next prime is 21008211863. The reversal of 21008211823 is 32811280012.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21008211823 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21008211791 and 21008211800.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21008211803) 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, 10504105911 + 10504105912.

It is an arithmetic number, because the mean of its divisors is an integer number (10504105912).

Almost surely, 2^21008211823 is an apocalyptic number.

21008211823 is a deficient number, since it is larger than the sum of its proper divisors (1).

21008211823 is an equidigital number, since it uses as much as digits as its factorization.

21008211823 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1536, while the sum is 28.

Adding to 21008211823 its reverse (32811280012), we get a palindrome (53819491835).

The spelling of 21008211823 in words is "twenty-one billion, eight million, two hundred eleven thousand, eight hundred twenty-three".