21549613 has 2 divisors, whose sum is σ = 21549614. Its totient is φ = 21549612.

The previous prime is 21549611. The next prime is 21549623. The reversal of 21549613 is 31694512.

21549613 = 3282² + 3283².

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 10778089 + 10771524 = 3283^2 + 3282^2 .

It is a cyclic number.

It is not a de Polignac number, because 21549613 - 2¹ = 21549611 is a prime.

Together with 21549611, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21549611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10774806 + 10774807.

It is an arithmetic number, because the mean of its divisors is an integer number (10774807).

Almost surely, 2^21549613 is an apocalyptic number.

21549613 is the 3283-rd centered square number.

It is an amenable number.

21549613 is a deficient number, since it is larger than the sum of its proper divisors (1).

21549613 is an equidigital number, since it uses as much as digits as its factorization.

21549613 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6480, while the sum is 31.

The square root of 21549613 is about 4642.1560723440. The cubic root of 21549613 is about 278.2786098047.

The spelling of 21549613 in words is "twenty-one million, five hundred forty-nine thousand, six hundred thirteen".