21765685536 has 216 divisors, whose sum is σ = 73362707964. Its totient is φ = 6101222400.

The previous prime is 21765685517. The next prime is 21765685541. The reversal of 21765685536 is 63558656712.

It is a happy number.

21765685536 is a `hidden beast` number, since 2 + 1 + 76 + 568 + 5 + 5 + 3 + 6 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 20608325136 + 1157360400 = 143556^2 + 34020^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 733386 + ... + 762486.

Almost surely, 2^21765685536 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21765685536, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36681353982).

21765685536 is an abundant number, since it is smaller than the sum of its proper divisors (51597022428).

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

21765685536 is a wasteful number, since it uses less digits than its factorization.

21765685536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29184 (or 29166 counting only the distinct ones).

The product of its digits is 9072000, while the sum is 54.

The spelling of 21765685536 in words is "twenty-one billion, seven hundred sixty-five million, six hundred eighty-five thousand, five hundred thirty-six".