21218610538 has 12 divisors (see below), whose sum is σ = 31937172678. Its totient is φ = 10573010480.

The previous prime is 21218610533. The next prime is 21218610577. The reversal of 21218610538 is 83501681212.

It can be written as a sum of positive squares in 3 ways, for example, as 20679302809 + 539307729 = 143803^2 + 23223^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21218610497 and 21218610506.

It is not an unprimeable number, because it can be changed into a prime (21218610533) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 109908 + ... + 233488.

Almost surely, 2^21218610538 is an apocalyptic number.

21218610538 is a deficient number, since it is larger than the sum of its proper divisors (10718562140).

21218610538 is an equidigital number, since it uses as much as digits as its factorization.

21218610538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124169 (or 123876 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 37.

The spelling of 21218610538 in words is "twenty-one billion, two hundred eighteen million, six hundred ten thousand, five hundred thirty-eight".