21968128 has 144 divisors (see below), whose sum is σ = 57689856. Its totient is φ = 8110080.

The previous prime is 21968117. The next prime is 21968143. The reversal of 21968128 is 82186912.

It is a Smith number, since the sum of its digits (37) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 535788 + ... + 535828.

It is an arithmetic number, because the mean of its divisors is an integer number (400624).

Almost surely, 2^21968128 is an apocalyptic number.

21968128 is a gapful number since it is divisible by the number (28) 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 21968128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28844928).

21968128 is an abundant number, since it is smaller than the sum of its proper divisors (35721728).

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

21968128 is a wasteful number, since it uses less digits than its factorization.

21968128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100 (or 86 counting only the distinct ones).

The product of its digits is 13824, while the sum is 37.

The square root of 21968128 is about 4687.0169617786. The cubic root of 21968128 is about 280.0685546424.

It can be divided in two parts, 2 and 1968128, that multiplied together give a square (3936256 = 1984²).

The spelling of 21968128 in words is "twenty-one million, nine hundred sixty-eight thousand, one hundred twenty-eight".