21423040 has 28 divisors (see below), whose sum is σ = 51014376. Its totient is φ = 8569088.

The previous prime is 21423019. The next prime is 21423053. The reversal of 21423040 is 4032412.

It is a Harshad number since it is a multiple of its sum of digits (16).

It is a congruent number.

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, 33154 + ... + 33793.

It is an arithmetic number, because the mean of its divisors is an integer number (1821942).

Almost surely, 2^21423040 is an apocalyptic number.

21423040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21423040 is an abundant number, since it is smaller than the sum of its proper divisors (29591336).

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

21423040 is an equidigital number, since it uses as much as digits as its factorization.

21423040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 66964 (or 66954 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 21423040 is about 4628.5029977305. The cubic root of 21423040 is about 277.7327106738.

Adding to 21423040 its reverse (4032412), we get a palindrome (25455452).

The spelling of 21423040 in words is "twenty-one million, four hundred twenty-three thousand, forty".