21021313 has 4 divisors (see below), whose sum is σ = 21031380. Its totient is φ = 21011248.

The previous prime is 21021293. The next prime is 21021323. The reversal of 21021313 is 31312012.

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 3448449 + 17572864 = 1857^2 + 4192^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021313 - 2¹⁷ = 20890241 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21021293 and 21021302.

It is not an unprimeable number, because it can be changed into a prime (21021323) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 598 + ... + 6511.

It is an arithmetic number, because the mean of its divisors is an integer number (5257845).

Almost surely, 2^21021313 is an apocalyptic number.

It is an amenable number.

21021313 is a deficient number, since it is larger than the sum of its proper divisors (10067).

21021313 is an equidigital number, since it uses as much as digits as its factorization.

21021313 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10066.

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

The square root of 21021313 is about 4584.9005441776. The cubic root of 21021313 is about 275.9857209234.

Adding to 21021313 its reverse (31312012), we get a palindrome (52333325).

The spelling of 21021313 in words is "twenty-one million, twenty-one thousand, three hundred thirteen".