66561005 has 16 divisors (see below), whose sum is σ = 91726464. Its totient is φ = 45420480.

The previous prime is 66560987. The next prime is 66561007. The reversal of 66561005 is 50016566.

66561005 = 1362² + 1363² + ... + 1396².

It is not a de Polignac number, because 66561005 - 2⁶ = 66560941 is a prime.

It is a super-2 number, since 2×66561005² = 8860734773220050, which contains 22 as substring.

It is a Smith number, since the sum of its digits (29) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66561007) 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 15 ways as a sum of consecutive naturals, for example, 2879 + ... + 11891.

It is an arithmetic number, because the mean of its divisors is an integer number (5732904).

Almost surely, 2^66561005 is an apocalyptic number.

It is an amenable number.

66561005 is a deficient number, since it is larger than the sum of its proper divisors (25165459).

66561005 is a wasteful number, since it uses less digits than its factorization.

66561005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9236.

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

The square root of 66561005 is about 8158.4928142396. The cubic root of 66561005 is about 405.2658012317.

The spelling of 66561005 in words is "sixty-six million, five hundred sixty-one thousand, five".