21978478578 has 16 divisors (see below), whose sum is σ = 50236522560. Its totient is φ = 6279565296.

The previous prime is 21978478537. The next prime is 21978478603. The reversal of 21978478578 is 87587487912.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 261648513 + ... + 261648596.

It is an arithmetic number, because the mean of its divisors is an integer number (3139782660).

Almost surely, 2^21978478578 is an apocalyptic number.

21978478578 is an abundant number, since it is smaller than the sum of its proper divisors (28258043982).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21978478578 is a wasteful number, since it uses less digits than its factorization.

21978478578 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 523297121.

The product of its digits is 63221760, while the sum is 66.

The spelling of 21978478578 in words is "twenty-one billion, nine hundred seventy-eight million, four hundred seventy-eight thousand, five hundred seventy-eight".