21878443645 has 16 divisors (see below), whose sum is σ = 27265677120. Its totient is φ = 16840543104.

The previous prime is 21878443637. The next prime is 21878443669. The reversal of 21878443645 is 54634487812.

It is a cyclic number.

It is not a de Polignac number, because 21878443645 - 2³ = 21878443637 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21878443592 and 21878443601.

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 15 ways as a sum of consecutive naturals, for example, 745000 + ... + 773809.

It is an arithmetic number, because the mean of its divisors is an integer number (1704104820).

Almost surely, 2^21878443645 is an apocalyptic number.

It is an amenable number.

21878443645 is a deficient number, since it is larger than the sum of its proper divisors (5387233475).

21878443645 is a wasteful number, since it uses less digits than its factorization.

21878443645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1518924.

The product of its digits is 5160960, while the sum is 52.

The spelling of 21878443645 in words is "twenty-one billion, eight hundred seventy-eight million, four hundred forty-three thousand, six hundred forty-five".