21261321 has 27 divisors (see below), whose sum is σ = 32417749. Its totient is φ = 13427232.

The previous prime is 21261293. The next prime is 21261337. The reversal of 21261321 is 12316212.

The square root of 21261321 is 4611.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 1334025 + 19927296 = 1155^2 + 4464^2 .

It is not a de Polignac number, because 21261321 - 2⁷ = 21261193 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21261294 and 21261303.

It is not an unprimeable number, because it can be changed into a prime (21260321) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 401131 + ... + 401183.

Almost surely, 2^21261321 is an apocalyptic number.

21261321 is the 4611-st square number.

21261321 is the 2306-th centered octagonal number.

It is an amenable number.

21261321 is a deficient number, since it is larger than the sum of its proper divisors (11156428).

21261321 is an equidigital number, since it uses as much as digits as its factorization.

21261321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 170 (or 85 counting only the distinct ones).

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

The cubic root of 21261321 is about 277.0320919258.

Multiplying 21261321 by its product of digits (144), we get a square (3061630224 = 55332²).

Adding to 21261321 its reverse (12316212), we get a palindrome (33577533).

The spelling of 21261321 in words is "twenty-one million, two hundred sixty-one thousand, three hundred twenty-one".