21968820 has 120 divisors (see below), whose sum is σ = 70253568. Its totient is φ = 5745600.

The previous prime is 21968819. The next prime is 21968867. The reversal of 21968820 is 2886912.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a plaindrome in base 11.

It is a zygodrome in base 11.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 114925 + ... + 115115.

Almost surely, 2^21968820 is an apocalyptic number.

21968820 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 21968820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35126784).

21968820 is an abundant number, since it is smaller than the sum of its proper divisors (48284748).

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

21968820 is a wasteful number, since it uses less digits than its factorization.

21968820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 283 (or 272 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 36.

The square root of 21968820 is about 4687.0907821377. The cubic root of 21968820 is about 280.0714953482.

The spelling of 21968820 in words is "twenty-one million, nine hundred sixty-eight thousand, eight hundred twenty".