21124321 has 2 divisors, whose sum is σ = 21124322. Its totient is φ = 21124320.

The previous prime is 21124289. The next prime is 21124339. The reversal of 21124321 is 12342112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17472400 + 3651921 = 4180^2 + 1911^2 .

It is a cyclic number.

It is not a de Polignac number, because 21124321 - 2⁵ = 21124289 is a prime.

It is a super-2 number, since 2×21124321² = 892473875422082, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21124295 and 21124304.

It is not a weakly prime, because it can be changed into another prime (21124351) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10562160 + 10562161.

It is an arithmetic number, because the mean of its divisors is an integer number (10562161).

Almost surely, 2^21124321 is an apocalyptic number.

It is an amenable number.

21124321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21124321 is an equidigital number, since it uses as much as digits as its factorization.

21124321 is an evil number, because the sum of its binary digits is even.

The product of its digits is 96, while the sum is 16.

The square root of 21124321 is about 4596.1202116568. The cubic root of 21124321 is about 276.4357788865.

Adding to 21124321 its reverse (12342112), we get a palindrome (33466433).

The spelling of 21124321 in words is "twenty-one million, one hundred twenty-four thousand, three hundred twenty-one".