66120521 has 4 divisors (see below), whose sum is σ = 67368132. Its totient is φ = 64872912.

The previous prime is 66120499. The next prime is 66120529. The reversal of 66120521 is 12502166.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 58308496 + 7812025 = 7636^2 + 2795^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-66120521 is a prime.

It is a super-2 number, since 2×66120521² = 8743846594622882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66120529) 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, 623726 + ... + 623831.

It is an arithmetic number, because the mean of its divisors is an integer number (16842033).

Almost surely, 2^66120521 is an apocalyptic number.

It is an amenable number.

66120521 is a deficient number, since it is larger than the sum of its proper divisors (1247611).

66120521 is a wasteful number, since it uses less digits than its factorization.

66120521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1247610.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 66120521 is about 8131.4525762621. The cubic root of 66120521 is about 404.3698394980.

Adding to 66120521 its reverse (12502166), we get a palindrome (78622687).

The spelling of 66120521 in words is "sixty-six million, one hundred twenty thousand, five hundred twenty-one".