21978478458 has 96 divisors (see below), whose sum is σ = 52097924736. Its totient is φ = 6669057024.

The previous prime is 21978478451. The next prime is 21978478463. The reversal of 21978478458 is 85487487912.

21978478458 is a `hidden beast` number, since 21 + 97 + 8 + 4 + 78 + 458 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 21978478395 and 21978478404.

It is not an unprimeable number, because it can be changed into a prime (21978478451) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 1347166 + ... + 1363382.

It is an arithmetic number, because the mean of its divisors is an integer number (542686716).

Almost surely, 2^21978478458 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21978478458, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26048962368).

21978478458 is an abundant number, since it is smaller than the sum of its proper divisors (30119446278).

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

21978478458 is a wasteful number, since it uses less digits than its factorization.

21978478458 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16388 (or 16385 counting only the distinct ones).

The product of its digits is 36126720, while the sum is 63.

The spelling of 21978478458 in words is "twenty-one billion, nine hundred seventy-eight million, four hundred seventy-eight thousand, four hundred fifty-eight".