21012321 has 16 divisors (see below), whose sum is σ = 30643200. Its totient is φ = 12701520.

The previous prime is 21012311. The next prime is 21012331. The reversal of 21012321 is 12321012.

21012321 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.

It is an interprime number because it is at equal distance from previous prime (21012311) and next prime (21012331).

It is not a de Polignac number, because 21012321 - 2⁷ = 21012193 is a prime.

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 = 21012297 and 21012306.

It is not an unprimeable number, because it can be changed into a prime (21012301) 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 15 ways as a sum of consecutive naturals, for example, 19236 + ... + 20298.

It is an arithmetic number, because the mean of its divisors is an integer number (1915200).

Almost surely, 2^21012321 is an apocalyptic number.

It is an amenable number.

21012321 is a deficient number, since it is larger than the sum of its proper divisors (9630879).

21012321 is a wasteful number, since it uses less digits than its factorization.

21012321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1676.

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21012321 is about 4583.9198291419. The cubic root of 21012321 is about 275.9463637634.

Adding to 21012321 its reverse (12321012), we get a palindrome (33333333).

The spelling of 21012321 in words is "twenty-one million, twelve thousand, three hundred twenty-one".