21093840 has 60 divisors (see below), whose sum is σ = 70842564. Its totient is φ = 5624832.

The previous prime is 21093833. The next prime is 21093899. The reversal of 21093840 is 4839012.

It can be written as a sum of positive squares in 2 ways, for example, as 11209104 + 9884736 = 3348^2 + 3144^2 .

It is a tau number, because it is divible by the number of its divisors (60).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13929 + ... + 15368.

Almost surely, 2^21093840 is an apocalyptic number.

21093840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21093840 is an abundant number, since it is smaller than the sum of its proper divisors (49748724).

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

21093840 is a wasteful number, since it uses less digits than its factorization.

21093840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29316 (or 29307 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21093840 is about 4592.8030656670. The cubic root of 21093840 is about 276.3027553608.

The spelling of 21093840 in words is "twenty-one million, ninety-three thousand, eight hundred forty".