21978478456 has 128 divisors (see below), whose sum is σ = 49683456000. Its totient is φ = 9002620800.

The previous prime is 21978478451. The next prime is 21978478463. The reversal of 21978478456 is 65487487912.

It is a super-2 number, since 2×21978478456² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21978478394 and 21978478403.

It is a congruent number.

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

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 3054495 + ... + 3061681.

It is an arithmetic number, because the mean of its divisors is an integer number (388152000).

Almost surely, 2^21978478456 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21978478456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24841728000).

21978478456 is an abundant number, since it is smaller than the sum of its proper divisors (27704977544).

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

21978478456 is a wasteful number, since it uses less digits than its factorization.

21978478456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7313 (or 7309 counting only the distinct ones).

The product of its digits is 27095040, while the sum is 61.

The spelling of 21978478456 in words is "twenty-one billion, nine hundred seventy-eight million, four hundred seventy-eight thousand, four hundred fifty-six".