21313021 has 2 divisors, whose sum is σ = 21313022. Its totient is φ = 21313020.

The previous prime is 21313001. The next prime is 21313037. The reversal of 21313021 is 12031312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21288996 + 24025 = 4614^2 + 155^2 .

It is a cyclic number.

It is not a de Polignac number, because 21313021 - 2¹⁵ = 21280253 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21312992 and 21313010.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21313001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656510 + 10656511.

It is an arithmetic number, because the mean of its divisors is an integer number (10656511).

Almost surely, 2^21313021 is an apocalyptic number.

It is an amenable number.

21313021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21313021 is an equidigital number, since it uses as much as digits as its factorization.

21313021 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21313021 is about 4616.6027552736. The cubic root of 21313021 is about 277.2564581302.

Adding to 21313021 its reverse (12031312), we get a palindrome (33344333).

The spelling of 21313021 in words is "twenty-one million, three hundred thirteen thousand, twenty-one".