66561523 has 4 divisors (see below), whose sum is σ = 76070320. Its totient is φ = 57052728.

The previous prime is 66561461. The next prime is 66561527. The reversal of 66561523 is 32516566.

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

It is a cyclic number.

It is not a de Polignac number, because 66561523 - 2²¹ = 64464371 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66561527) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4754388 + ... + 4754401.

It is an arithmetic number, because the mean of its divisors is an integer number (19017580).

Almost surely, 2^66561523 is an apocalyptic number.

66561523 is a deficient number, since it is larger than the sum of its proper divisors (9508797).

66561523 is an equidigital number, since it uses as much as digits as its factorization.

66561523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9508796.

The product of its digits is 32400, while the sum is 34.

The square root of 66561523 is about 8158.5245602376. The cubic root of 66561523 is about 405.2668525337.

The spelling of 66561523 in words is "sixty-six million, five hundred sixty-one thousand, five hundred twenty-three".