21033121 has 2 divisors, whose sum is σ = 21033122. Its totient is φ = 21033120.

The previous prime is 21033119. The next prime is 21033127. The reversal of 21033121 is 12133012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20802721 + 230400 = 4561^2 + 480^2 .

It is a cyclic number.

It is not a de Polignac number, because 21033121 - 2¹ = 21033119 is a prime.

Together with 21033119, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21033127) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10516560 + 10516561.

It is an arithmetic number, because the mean of its divisors is an integer number (10516561).

Almost surely, 2^21033121 is an apocalyptic number.

It is an amenable number.

21033121 is a deficient number, since it is larger than the sum of its proper divisors (1).

21033121 is an equidigital number, since it uses as much as digits as its factorization.

21033121 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 21033121 is about 4586.1880685380. The cubic root of 21033121 is about 276.0373864149.

Adding to 21033121 its reverse (12133012), we get a palindrome (33166133).

The spelling of 21033121 in words is "twenty-one million, thirty-three thousand, one hundred twenty-one".