66521549 has 2 divisors, whose sum is σ = 66521550. Its totient is φ = 66521548.

The previous prime is 66521513. The next prime is 66521551. The reversal of 66521549 is 94512566.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 62884900 + 3636649 = 7930^2 + 1907^2 .

It is a cyclic number.

It is not a de Polignac number, because 66521549 - 2²⁴ = 49744333 is a prime.

Together with 66521551, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66521509) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 33260774 + 33260775.

It is an arithmetic number, because the mean of its divisors is an integer number (33260775).

Almost surely, 2^66521549 is an apocalyptic number.

It is an amenable number.

66521549 is a deficient number, since it is larger than the sum of its proper divisors (1).

66521549 is an equidigital number, since it uses as much as digits as its factorization.

66521549 is an evil number, because the sum of its binary digits is even.

The product of its digits is 64800, while the sum is 38.

The square root of 66521549 is about 8156.0743620936. The cubic root of 66521549 is about 405.1857076492.

The spelling of 66521549 in words is "sixty-six million, five hundred twenty-one thousand, five hundred forty-nine".