21016613 has 2 divisors, whose sum is σ = 21016614. Its totient is φ = 21016612.

The previous prime is 21016609. The next prime is 21016631. The reversal of 21016613 is 31661012.

Together with next prime (21016631) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16826404 + 4190209 = 4102^2 + 2047^2 .

It is a cyclic number.

It is not a de Polignac number, because 21016613 - 2² = 21016609 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21016643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10508306 + 10508307.

It is an arithmetic number, because the mean of its divisors is an integer number (10508307).

Almost surely, 2^21016613 is an apocalyptic number.

It is an amenable number.

21016613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21016613 is an equidigital number, since it uses as much as digits as its factorization.

21016613 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 21016613 is about 4584.3879635127. The cubic root of 21016613 is about 275.9651508545.

Adding to 21016613 its reverse (31661012), we get a palindrome (52677625).

The spelling of 21016613 in words is "twenty-one million, sixteen thousand, six hundred thirteen".