21918193920 has 864 divisors, whose sum is σ = 92863008000. Its totient is φ = 4893364224.

The previous prime is 21918193901. The next prime is 21918193931. The reversal of 21918193920 is 2939181912.

It is a tau number, because it is divible by the number of its divisors (864).

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

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 95 ways as a sum of consecutive naturals, for example, 509725419 + ... + 509725461.

Almost surely, 2^21918193920 is an apocalyptic number.

21918193920 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 21918193920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46431504000).

21918193920 is an abundant number, since it is smaller than the sum of its proper divisors (70944814080).

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

21918193920 is an frugal number, since it uses more digits than its factorization.

21918193920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137 (or 60 counting only the distinct ones).

The product of its (nonzero) digits is 69984, while the sum is 45.

The spelling of 21918193920 in words is "twenty-one billion, nine hundred eighteen million, one hundred ninety-three thousand, nine hundred twenty".