21620213 has 4 divisors (see below), whose sum is σ = 21667980. Its totient is φ = 21572448.

The previous prime is 21620197. The next prime is 21620227. The reversal of 21620213 is 31202612.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10484644 + 11135569 = 3238^2 + 3337^2 .

It is a cyclic number.

It is not a de Polignac number, because 21620213 - 2⁴ = 21620197 is a prime.

It is a super-2 number, since 2×21620213² = 934867220330738, 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 = 21620191 and 21620200.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21620273) 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, 23198 + ... + 24111.

It is an arithmetic number, because the mean of its divisors is an integer number (5416995).

Almost surely, 2^21620213 is an apocalyptic number.

It is an amenable number.

21620213 is a deficient number, since it is larger than the sum of its proper divisors (47767).

21620213 is an equidigital number, since it uses as much as digits as its factorization.

21620213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 47766.

The product of its (nonzero) digits is 144, while the sum is 17.

The square root of 21620213 is about 4649.7540795186. The cubic root of 21620213 is about 278.5821737066.

Adding to 21620213 its reverse (31202612), we get a palindrome (52822825).

The spelling of 21620213 in words is "twenty-one million, six hundred twenty thousand, two hundred thirteen".