21270321 has 12 divisors (see below), whose sum is σ = 30785040. Its totient is φ = 14151960.

The previous prime is 21270307. The next prime is 21270323. The reversal of 21270321 is 12307212.

It is not a de Polignac number, because 21270321 - 2¹⁴ = 21253937 is a prime.

It is a super-3 number, since 3×21270321³ (a number of 23 digits) contains 333 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21270294 and 21270303.

It is not an unprimeable number, because it can be changed into a prime (21270323) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 3070 + ... + 7208.

It is an arithmetic number, because the mean of its divisors is an integer number (2565420).

Almost surely, 2^21270321 is an apocalyptic number.

It is an amenable number.

21270321 is a deficient number, since it is larger than the sum of its proper divisors (9514719).

21270321 is a wasteful number, since it uses less digits than its factorization.

21270321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4716 (or 4713 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 21270321 is about 4611.9758238742. The cubic root of 21270321 is about 277.0711759994.

Adding to 21270321 its reverse (12307212), we get a palindrome (33577533).

The spelling of 21270321 in words is "twenty-one million, two hundred seventy thousand, three hundred twenty-one".