21031321 has 4 divisors (see below), whose sum is σ = 21111552. Its totient is φ = 20951092.

The previous prime is 21031313. The next prime is 21031333. The reversal of 21031321 is 12313012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21031321 - 2³ = 21031313 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21031391) 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 3 ways as a sum of consecutive naturals, for example, 39721 + ... + 40246.

It is an arithmetic number, because the mean of its divisors is an integer number (5277888).

Almost surely, 2^21031321 is an apocalyptic number.

It is an amenable number.

21031321 is a deficient number, since it is larger than the sum of its proper divisors (80231).

21031321 is an equidigital number, since it uses as much as digits as its factorization.

21031321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80230.

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

The square root of 21031321 is about 4585.9918229321. The cubic root of 21031321 is about 276.0295118271.

Adding to 21031321 its reverse (12313012), we get a palindrome (33344333).

The spelling of 21031321 in words is "twenty-one million, thirty-one thousand, three hundred twenty-one".