21684747518 has 16 divisors (see below), whose sum is σ = 37184348544. Its totient is φ = 9290839320.

The previous prime is 21684747517. The next prime is 21684747523. The reversal of 21684747518 is 81574748612.

It is a Smith number, since the sum of its digits (53) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 21684747518.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21684747517) 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 in 7 ways as a sum of consecutive naturals, for example, 166880 + ... + 266867.

It is an arithmetic number, because the mean of its divisors is an integer number (2324021784).

Almost surely, 2^21684747518 is an apocalyptic number.

21684747518 is a deficient number, since it is larger than the sum of its proper divisors (15499601026).

21684747518 is a wasteful number, since it uses less digits than its factorization.

21684747518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 437327.

The product of its digits is 3010560, while the sum is 53.

The spelling of 21684747518 in words is "twenty-one billion, six hundred eighty-four million, seven hundred forty-seven thousand, five hundred eighteen".