21978241920 has 672 divisors, whose sum is σ = 84196456920. Its totient is φ = 5482266624.

The previous prime is 21978241897. The next prime is 21978241949. The reversal of 21978241920 is 2914287912.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 83 ways as a sum of consecutive naturals, for example, 134835759 + ... + 134835921.

Almost surely, 2^21978241920 is an apocalyptic number.

21978241920 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 21978241920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42098228460).

21978241920 is an abundant number, since it is smaller than the sum of its proper divisors (62218215000).

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

21978241920 is an equidigital number, since it uses as much as digits as its factorization.

21978241920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 234 (or 190 counting only the distinct ones).

The product of its (nonzero) digits is 145152, while the sum is 45.

The spelling of 21978241920 in words is "twenty-one billion, nine hundred seventy-eight million, two hundred forty-one thousand, nine hundred twenty".