21709578816 has 84 divisors (see below), whose sum is σ = 65887005132. Its totient is φ = 6810845184.

The previous prime is 21709578811. The next prime is 21709578841. The reversal of 21709578816 is 61887590712.

It can be written as a sum of positive squares in 2 ways, for example, as 8299938816 + 13409640000 = 91104^2 + 115800^2 .

It is not an unprimeable number, because it can be changed into a prime (21709578811) 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 in 11 ways as a sum of consecutive naturals, for example, 1098745 + ... + 1118328.

Almost surely, 2^21709578816 is an apocalyptic number.

It is an amenable number.

21709578816 is an abundant number, since it is smaller than the sum of its proper divisors (44177426316).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21709578816 is a wasteful number, since it uses less digits than its factorization.

21709578816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2217108 (or 2217095 counting only the distinct ones).

The product of its (nonzero) digits is 1693440, while the sum is 54.

The spelling of 21709578816 in words is "twenty-one billion, seven hundred nine million, five hundred seventy-eight thousand, eight hundred sixteen".