21788320 has 24 divisors (see below), whose sum is σ = 51475284. Its totient is φ = 8715264.

The previous prime is 21788297. The next prime is 21788341. The reversal of 21788320 is 2388712.

It can be written as a sum of positive squares in 2 ways, for example, as 19749136 + 2039184 = 4444^2 + 1428^2 .

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 67929 + ... + 68248.

Almost surely, 2^21788320 is an apocalyptic number.

21788320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21788320 is an abundant number, since it is smaller than the sum of its proper divisors (29686964).

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

21788320 is a wasteful number, since it uses less digits than its factorization.

21788320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 136192 (or 136184 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 31.

The square root of 21788320 is about 4667.7960538138. The cubic root of 21788320 is about 279.3023447806.

The spelling of 21788320 in words is "twenty-one million, seven hundred eighty-eight thousand, three hundred twenty".