21189666788 has 6 divisors (see below), whose sum is σ = 37081916886. Its totient is φ = 10594833392.

The previous prime is 21189666787. The next prime is 21189666793. The reversal of 21189666788 is 88766698112.

It can be written as a sum of positive squares in only one way, i.e., 21169668004 + 19998784 = 145498^2 + 4472^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21189666788.

It is not an unprimeable number, because it can be changed into a prime (21189666787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2648708345 + ... + 2648708352.

It is an arithmetic number, because the mean of its divisors is an integer number (6180319481).

Almost surely, 2^21189666788 is an apocalyptic number.

It is an amenable number.

21189666788 is a deficient number, since it is larger than the sum of its proper divisors (15892250098).

21189666788 is a wasteful number, since it uses less digits than its factorization.

21189666788 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5297416701 (or 5297416699 counting only the distinct ones).

The product of its digits is 13934592, while the sum is 62.

The spelling of 21189666788 in words is "twenty-one billion, one hundred eighty-nine million, six hundred sixty-six thousand, seven hundred eighty-eight".