21878521478 has 16 divisors (see below), whose sum is σ = 35824965120. Its totient is φ = 9938185800.

The previous prime is 21878521477. The next prime is 21878521493. The reversal of 21878521478 is 87412587812.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21878521477) by changing a digit.

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, 295838 + ... + 362321.

It is an arithmetic number, because the mean of its divisors is an integer number (2239060320).

Almost surely, 2^21878521478 is an apocalyptic number.

21878521478 is a deficient number, since it is larger than the sum of its proper divisors (13946443642).

21878521478 is a wasteful number, since it uses less digits than its factorization.

21878521478 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 659683.

The product of its digits is 2007040, while the sum is 53.

The spelling of 21878521478 in words is "twenty-one billion, eight hundred seventy-eight million, five hundred twenty-one thousand, four hundred seventy-eight".