66135621 has 4 divisors (see below), whose sum is σ = 88180832. Its totient is φ = 44090412.

The previous prime is 66135611. The next prime is 66135647. The reversal of 66135621 is 12653166.

66135621 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.

It is not a de Polignac number, because 66135621 - 2¹⁰ = 66134597 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66135611) 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, 11022601 + ... + 11022606.

It is an arithmetic number, because the mean of its divisors is an integer number (22045208).

Almost surely, 2^66135621 is an apocalyptic number.

It is an amenable number.

66135621 is a deficient number, since it is larger than the sum of its proper divisors (22045211).

66135621 is a wasteful number, since it uses less digits than its factorization.

66135621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22045210.

The product of its digits is 6480, while the sum is 30.

The square root of 66135621 is about 8132.3810166519. The cubic root of 66135621 is about 404.4006192506.

Adding to 66135621 its reverse (12653166), we get a palindrome (78788787).

The spelling of 66135621 in words is "sixty-six million, one hundred thirty-five thousand, six hundred twenty-one".