21126321 has 6 divisors (see below), whose sum is σ = 30515810. Its totient is φ = 14084208.

The previous prime is 21126317. The next prime is 21126337. The reversal of 21126321 is 12362112.

21126321 is a `hidden beast` number, since 21 + 12 + 632 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 19927296 + 1199025 = 4464^2 + 1095^2 .

It is not a de Polignac number, because 21126321 - 2² = 21126317 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21126294 and 21126303.

It is not an unprimeable number, because it can be changed into a prime (21126341) 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 5 ways as a sum of consecutive naturals, for example, 1173676 + ... + 1173693.

Almost surely, 2^21126321 is an apocalyptic number.

It is an amenable number.

21126321 is a deficient number, since it is larger than the sum of its proper divisors (9389489).

21126321 is a wasteful number, since it uses less digits than its factorization.

21126321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2347375 (or 2347372 counting only the distinct ones).

The product of its digits is 144, while the sum is 18.

The square root of 21126321 is about 4596.3377813211. The cubic root of 21126321 is about 276.4445027031. Note that the first 3 decimals are identical.

Adding to 21126321 its reverse (12362112), we get a palindrome (33488433).

The spelling of 21126321 in words is "twenty-one million, one hundred twenty-six thousand, three hundred twenty-one".