21330031 has 4 divisors (see below), whose sum is σ = 21498112. Its totient is φ = 21161952.

The previous prime is 21329999. The next prime is 21330047. The reversal of 21330031 is 13003312.

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 21330031 - 2⁵ = 21329999 is a prime.

It is a super-2 number, since 2×21330031² = 909940444921922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21329993 and 21330020.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21370031) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 83850 + ... + 84103.

It is an arithmetic number, because the mean of its divisors is an integer number (5374528).

Almost surely, 2^21330031 is an apocalyptic number.

21330031 is a deficient number, since it is larger than the sum of its proper divisors (168081).

21330031 is a wasteful number, since it uses less digits than its factorization.

21330031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 168080.

The product of its (nonzero) digits is 54, while the sum is 13.

The square root of 21330031 is about 4618.4446516116. Note that the first 3 decimals coincide. The cubic root of 21330031 is about 277.3301983140.

Adding to 21330031 its reverse (13003312), we get a palindrome (34333343).

The spelling of 21330031 in words is "twenty-one million, three hundred thirty thousand, thirty-one".