21685144778 has 32 divisors (see below), whose sum is σ = 36616840128. Its totient is φ = 9544953600.

The previous prime is 21685144757. The next prime is 21685144787. The reversal of 21685144778 is 87744158612.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 108626 + ... + 234882.

It is an arithmetic number, because the mean of its divisors is an integer number (1144276254).

Almost surely, 2^21685144778 is an apocalyptic number.

21685144778 is a deficient number, since it is larger than the sum of its proper divisors (14931695350).

21685144778 is a wasteful number, since it uses less digits than its factorization.

21685144778 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126518.

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

The spelling of 21685144778 in words is "twenty-one billion, six hundred eighty-five million, one hundred forty-four thousand, seven hundred seventy-eight".