21087744 has 40 divisors (see below), whose sum is σ = 56183160. Its totient is φ = 7028736.

The previous prime is 21087713. The next prime is 21087751. The reversal of 21087744 is 44778012.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5329 + ... + 8400.

It is an arithmetic number, because the mean of its divisors is an integer number (1404579).

Almost surely, 2^21087744 is an apocalyptic number.

21087744 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21087744 is an abundant number, since it is smaller than the sum of its proper divisors (35095416).

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

21087744 is an equidigital number, since it uses as much as digits as its factorization.

21087744 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13750 (or 13734 counting only the distinct ones).

The product of its (nonzero) digits is 12544, while the sum is 33.

The square root of 21087744 is about 4592.1393707073. The cubic root of 21087744 is about 276.2761361539.

The spelling of 21087744 in words is "twenty-one million, eighty-seven thousand, seven hundred forty-four".