21518542823 has 2 divisors, whose sum is σ = 21518542824. Its totient is φ = 21518542822.

The previous prime is 21518542811. The next prime is 21518542867. The reversal of 21518542823 is 32824581512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21518542823 - 2¹⁴ = 21518526439 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21518541823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10759271411 + 10759271412.

It is an arithmetic number, because the mean of its divisors is an integer number (10759271412).

Almost surely, 2^21518542823 is an apocalyptic number.

21518542823 is a deficient number, since it is larger than the sum of its proper divisors (1).

21518542823 is an equidigital number, since it uses as much as digits as its factorization.

21518542823 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 153600, while the sum is 41.

Adding to 21518542823 its sum of digits (41), we get a square (21518542864 = 146692²).

The spelling of 21518542823 in words is "twenty-one billion, five hundred eighteen million, five hundred forty-two thousand, eight hundred twenty-three".