21645023738 has 16 divisors (see below), whose sum is σ = 35220263400. Its totient is φ = 9917089536.

The previous prime is 21645023677. The next prime is 21645023753. The reversal of 21645023738 is 83732054612.

It can be written as a sum of positive squares in 4 ways, for example, as 17834801209 + 3810222529 = 133547^2 + 61727^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21645023695 and 21645023704.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 3034763 + ... + 3041886.

Almost surely, 2^21645023738 is an apocalyptic number.

21645023738 is a deficient number, since it is larger than the sum of its proper divisors (13575239662).

21645023738 is a wasteful number, since it uses less digits than its factorization.

21645023738 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6076801.

The product of its (nonzero) digits is 241920, while the sum is 41.

The spelling of 21645023738 in words is "twenty-one billion, six hundred forty-five million, twenty-three thousand, seven hundred thirty-eight".