21993680 has 40 divisors (see below), whose sum is σ = 51726600. Its totient is φ = 8695808.

The previous prime is 21993677. The next prime is 21993691. The reversal of 21993680 is 8639912.

It can be written as a sum of positive squares in 4 ways, for example, as 3400336 + 18593344 = 1844^2 + 4312^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5576 + ... + 8664.

It is an arithmetic number, because the mean of its divisors is an integer number (1293165).

Almost surely, 2^21993680 is an apocalyptic number.

21993680 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 21993680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25863300).

21993680 is an abundant number, since it is smaller than the sum of its proper divisors (29732920).

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

21993680 is a wasteful number, since it uses less digits than its factorization.

21993680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3191 (or 3185 counting only the distinct ones).

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 21993680 is about 4689.7419971679. The cubic root of 21993680 is about 280.1770988464.

The spelling of 21993680 in words is "twenty-one million, nine hundred ninety-three thousand, six hundred eighty".