21005313 has 8 divisors (see below), whose sum is σ = 32008128. Its totient is φ = 12003024.

The previous prime is 21005311. The next prime is 21005329. The reversal of 21005313 is 31350012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21005313 - 2¹ = 21005311 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21005292 and 21005301.

It is not an unprimeable number, because it can be changed into a prime (21005311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 500106 + ... + 500147.

It is an arithmetic number, because the mean of its divisors is an integer number (4001016).

Almost surely, 2^21005313 is an apocalyptic number.

It is an amenable number.

21005313 is a deficient number, since it is larger than the sum of its proper divisors (11002815).

21005313 is a wasteful number, since it uses less digits than its factorization.

21005313 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1000263.

The product of its (nonzero) digits is 90, while the sum is 15.

The square root of 21005313 is about 4583.1553541201. The cubic root of 21005313 is about 275.9156826034.

Adding to 21005313 its reverse (31350012), we get a palindrome (52355325).

The spelling of 21005313 in words is "twenty-one million, five thousand, three hundred thirteen".