21748321 has 16 divisors (see below), whose sum is σ = 26490240. Its totient is φ = 17429760.

The previous prime is 21748313. The next prime is 21748333. The reversal of 21748321 is 12384712.

It is not a de Polignac number, because 21748321 - 2³ = 21748313 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21748321.

It is not an unprimeable number, because it can be changed into a prime (21748351) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20791 + ... + 21811.

It is an arithmetic number, because the mean of its divisors is an integer number (1655640).

Almost surely, 2^21748321 is an apocalyptic number.

It is an amenable number.

21748321 is a deficient number, since it is larger than the sum of its proper divisors (4741919).

21748321 is a wasteful number, since it uses less digits than its factorization.

21748321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1224.

The product of its digits is 2688, while the sum is 28.

The square root of 21748321 is about 4663.5095153757. The cubic root of 21748321 is about 279.1313256616.

The spelling of 21748321 in words is "twenty-one million, seven hundred forty-eight thousand, three hundred twenty-one".