21978271980 has 144 divisors (see below), whose sum is σ = 76228536384. Its totient is φ = 5021153280.

The previous prime is 21978271961. The next prime is 21978271999. The reversal of 21978271980 is 8917287912.

21978271980 is a `hidden beast` number, since 219 + 78 + 271 + 98 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (21978271961) and next prime (21978271999).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 4323040 + ... + 4328120.

It is an arithmetic number, because the mean of its divisors is an integer number (529364836).

Almost surely, 2^21978271980 is an apocalyptic number.

21978271980 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21978271980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38114268192).

21978271980 is an abundant number, since it is smaller than the sum of its proper divisors (54250264404).

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

21978271980 is a wasteful number, since it uses less digits than its factorization.

21978271980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8536 (or 8531 counting only the distinct ones).

The product of its (nonzero) digits is 1016064, while the sum is 54.

The spelling of 21978271980 in words is "twenty-one billion, nine hundred seventy-eight million, two hundred seventy-one thousand, nine hundred eighty".