66105521 has 4 divisors (see below), whose sum is σ = 66202992. Its totient is φ = 66008052.

The previous prime is 66105511. The next prime is 66105527. The reversal of 66105521 is 12550166.

66105521 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12550166 = 2 ⋅6275083.

It is a cyclic number.

It is not a de Polignac number, because 66105521 - 2¹⁴ = 66089137 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (66105527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 47711 + ... + 49076.

It is an arithmetic number, because the mean of its divisors is an integer number (16550748).

Almost surely, 2^66105521 is an apocalyptic number.

It is an amenable number.

66105521 is a deficient number, since it is larger than the sum of its proper divisors (97471).

66105521 is an equidigital number, since it uses as much as digits as its factorization.

66105521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 97470.

The product of its (nonzero) digits is 1800, while the sum is 26.

The square root of 66105521 is about 8130.5301795147. The cubic root of 66105521 is about 404.3392589449.

Adding to 66105521 its reverse (12550166), we get a palindrome (78655687).

The spelling of 66105521 in words is "sixty-six million, one hundred five thousand, five hundred twenty-one".