21738439845 has 54 divisors (see below), whose sum is σ = 38989646514. Its totient is φ = 11204015040.

The previous prime is 21738439747. The next prime is 21738439889. The reversal of 21738439845 is 54893483712.

It is a happy number.

21738439845 is a `hidden beast` number, since 2 + 173 + 84 + 398 + 4 + 5 = 666.

It can be written as a sum of positive squares in 3 ways, for example, as 174398436 + 21564041409 = 13206^2 + 146847^2 .

It is not a de Polignac number, because 21738439845 - 2⁸ = 21738439589 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21738439791 and 21738439800.

It is a congruent number.

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 53 ways as a sum of consecutive naturals, for example, 30660351 + ... + 30661059.

It is an arithmetic number, because the mean of its divisors is an integer number (722030491).

Almost surely, 2^21738439845 is an apocalyptic number.

It is an amenable number.

21738439845 is a deficient number, since it is larger than the sum of its proper divisors (17251206669).

21738439845 is an frugal number, since it uses more digits than its factorization.

21738439845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1491 (or 748 counting only the distinct ones).

The product of its digits is 5806080, while the sum is 54.

The spelling of 21738439845 in words is "twenty-one billion, seven hundred thirty-eight million, four hundred thirty-nine thousand, eight hundred forty-five".