21210613 has 4 divisors (see below), whose sum is σ = 21248460. Its totient is φ = 21172768.

The previous prime is 21210587. The next prime is 21210619. The reversal of 21210613 is 31601212.

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 1077444 + 20133169 = 1038^2 + 4487^2 .

It is a cyclic number.

It is not a de Polignac number, because 21210613 - 2¹³ = 21202421 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210619) 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, 18070 + ... + 19207.

It is an arithmetic number, because the mean of its divisors is an integer number (5312115).

Almost surely, 2^21210613 is an apocalyptic number.

It is an amenable number.

21210613 is a deficient number, since it is larger than the sum of its proper divisors (37847).

21210613 is an equidigital number, since it uses as much as digits as its factorization.

21210613 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37846.

The product of its (nonzero) digits is 72, while the sum is 16.

The square root of 21210613 is about 4605.4981272388. The cubic root of 21210613 is about 276.8116771793.

Adding to 21210613 its reverse (31601212), we get a palindrome (52811825).

The spelling of 21210613 in words is "twenty-one million, two hundred ten thousand, six hundred thirteen".