21636223816 has 32 divisors (see below), whose sum is σ = 44001944280. Its totient is φ = 9933414400.

The previous prime is 21636223813. The next prime is 21636223823. The reversal of 21636223816 is 61832263612.

It can be written as a sum of positive squares in 4 ways, for example, as 18454135716 + 3182088100 = 135846^2 + 56410^2 .

It is not an unprimeable number, because it can be changed into a prime (21636223811) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1934545 + ... + 1945696.

Almost surely, 2^21636223816 is an apocalyptic number.

It is an amenable number.

21636223816 is an abundant number, since it is smaller than the sum of its proper divisors (22365720464).

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

21636223816 is a wasteful number, since it uses less digits than its factorization.

21636223816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3880305 (or 3880301 counting only the distinct ones).

The product of its digits is 124416, while the sum is 40.

The spelling of 21636223816 in words is "twenty-one billion, six hundred thirty-six million, two hundred twenty-three thousand, eight hundred sixteen".