21685781760 has 72 divisors (see below), whose sum is σ = 69258977760. Its totient is φ = 5782874112.

The previous prime is 21685781753. The next prime is 21685781783. The reversal of 21685781760 is 6718758612.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2819830 + ... + 2827509.

Almost surely, 2^21685781760 is an apocalyptic number.

21685781760 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21685781760 is an abundant number, since it is smaller than the sum of its proper divisors (47573196000).

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

21685781760 is an equidigital number, since it uses as much as digits as its factorization.

21685781760 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5647363 (or 5647349 counting only the distinct ones).

The product of its (nonzero) digits is 1128960, while the sum is 51.

The spelling of 21685781760 in words is "twenty-one billion, six hundred eighty-five million, seven hundred eighty-one thousand, seven hundred sixty".