66135521 has 4 divisors (see below), whose sum is σ = 66279444. Its totient is φ = 65991600.

The previous prime is 66135497. The next prime is 66135527. The reversal of 66135521 is 12553166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12553166 = 2 ⋅6276583.

It can be written as a sum of positive squares in 2 ways, for example, as 38688400 + 27447121 = 6220^2 + 5239^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66135521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66135527) 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, 71270 + ... + 72191.

It is an arithmetic number, because the mean of its divisors is an integer number (16569861).

Almost surely, 2^66135521 is an apocalyptic number.

It is an amenable number.

66135521 is a deficient number, since it is larger than the sum of its proper divisors (143923).

66135521 is a wasteful number, since it uses less digits than its factorization.

66135521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 143922.

The product of its digits is 5400, while the sum is 29.

The square root of 66135521 is about 8132.3748683887. The cubic root of 66135521 is about 404.4004154266.

Adding to 66135521 its reverse (12553166), we get a palindrome (78688687).

The spelling of 66135521 in words is "sixty-six million, one hundred thirty-five thousand, five hundred twenty-one".