21001313 has 4 divisors (see below), whose sum is σ = 21012420.
Its totient is φ = 20990208.
The previous prime is 21001247. The next prime is 21001319. The reversal of 21001313 is 31310012.
It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.
It can be written as a sum of positive squares in 2 ways, for example, as 19784704 + 1216609 = 4448^2 + 1103^2
It is a cyclic number.
It is not a de Polignac number, because 21001313 - 212 = 20997217 is a prime.
It is a Duffinian number.
It is a junction number, because it is equal to n+sod(n) for n = 21001294 and 21001303.
It is not an unprimeable number, because it can be changed into a prime (21001319) 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, 1928 + ... + 6761.
It is an arithmetic number, because the mean of its divisors is an integer number (5253105).
Almost surely, 221001313 is an apocalyptic number.
It is an amenable number.
21001313 is a deficient number, since it is larger than the sum of its proper divisors (11107).
21001313 is an equidigital number, since it uses as much as digits as its factorization.
21001313 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 11106.
The product of its (nonzero) digits is 18, while the sum is 11.
The square root of 21001313 is about 4582.7189527616.
The cubic root of 21001313 is about 275.8981674666.
Adding to 21001313 its reverse (31310012), we get a palindrome (52311325).
The spelling of 21001313 in words is "twenty-one million, one thousand, three hundred thirteen".