21623680 has 128 divisors (see below), whose sum is σ = 58605120. Its totient is φ = 7569408.

The previous prime is 21623663. The next prime is 21623681. The reversal of 21623680 is 8632612.

It is a tau number, because it is divible by the number of its divisors (128).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21623681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 191304 + ... + 191416.

Almost surely, 2^21623680 is an apocalyptic number.

21623680 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 21623680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29302560).

21623680 is an abundant number, since it is smaller than the sum of its proper divisors (36981440).

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

21623680 is a wasteful number, since it uses less digits than its factorization.

21623680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 168 (or 156 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 28.

The square root of 21623680 is about 4650.1268799894. The cubic root of 21623680 is about 278.5970639819.

The spelling of 21623680 in words is "twenty-one million, six hundred twenty-three thousand, six hundred eighty".