21331331 has 4 divisors (see below), whose sum is σ = 24378672. Its totient is φ = 18283992.

The previous prime is 21331313. The next prime is 21331333. The reversal of 21331331 is 13313312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21331331 - 2⁶ = 21331267 is a prime.

It is a super-2 number, since 2×21331331² = 910051364463122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21331333) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1523660 + ... + 1523673.

It is an arithmetic number, because the mean of its divisors is an integer number (6094668).

Almost surely, 2^21331331 is an apocalyptic number.

21331331 is a deficient number, since it is larger than the sum of its proper divisors (3047341).

21331331 is an equidigital number, since it uses as much as digits as its factorization.

21331331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3047340.

The product of its digits is 162, while the sum is 17.

The square root of 21331331 is about 4618.5853894889. The cubic root of 21331331 is about 277.3358323413.

Adding to 21331331 its reverse (13313312), we get a palindrome (34644643).

It can be divided in two parts, 2 and 1331331, that multiplied together give a palindrome (2662662).

The spelling of 21331331 in words is "twenty-one million, three hundred thirty-one thousand, three hundred thirty-one".