66561013 has 2 divisors, whose sum is σ = 66561014. Its totient is φ = 66561012.

The previous prime is 66561007. The next prime is 66561029. The reversal of 66561013 is 31016566.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 65173329 + 1387684 = 8073^2 + 1178^2 .

It is a cyclic number.

It is not a de Polignac number, because 66561013 - 2¹³ = 66552821 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (66561073) 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 as a sum of consecutive naturals, namely, 33280506 + 33280507.

It is an arithmetic number, because the mean of its divisors is an integer number (33280507).

Almost surely, 2^66561013 is an apocalyptic number.

It is an amenable number.

66561013 is a deficient number, since it is larger than the sum of its proper divisors (1).

66561013 is an equidigital number, since it uses as much as digits as its factorization.

66561013 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3240, while the sum is 28.

The square root of 66561013 is about 8158.4933045263. The cubic root of 66561013 is about 405.2658174681.

Adding to 66561013 its reverse (31016566), we get a palindrome (97577579).

The spelling of 66561013 in words is "sixty-six million, five hundred sixty-one thousand, thirteen".