21235840 has 32 divisors (see below), whose sum is σ = 50768460. Its totient is φ = 8494080.

The previous prime is 21235829. The next prime is 21235843. The reversal of 21235840 is 4853212.

It can be written as a sum of positive squares in 2 ways, for example, as 21013056 + 222784 = 4584^2 + 472^2 .

It is a tau number, because it is divible by the number of its divisors (32).

It is not an unprimeable number, because it can be changed into a prime (21235843) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15951 + ... + 17230.

Almost surely, 2^21235840 is an apocalyptic number.

21235840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21235840 is an abundant number, since it is smaller than the sum of its proper divisors (29532620).

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

21235840 is an equidigital number, since it uses as much as digits as its factorization.

21235840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33200 (or 33188 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 25.

The square root of 21235840 is about 4608.2361050623. The cubic root of 21235840 is about 276.9213763745.

The spelling of 21235840 in words is "twenty-one million, two hundred thirty-five thousand, eight hundred forty".