66555253561 has 4 divisors (see below), whose sum is σ = 66927070800. Its totient is φ = 66183436324.

The previous prime is 66555253559. The next prime is 66555253603. The reversal of 66555253561 is 16535255566.

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, and also an emirpimes, since its reverse is a distinct semiprime: 16535255566 = 2 ⋅8267627783.

It is a cyclic number.

It is not a de Polignac number, because 66555253561 - 2¹ = 66555253559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66555251561) 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, 185908351 + ... + 185908708.

It is an arithmetic number, because the mean of its divisors is an integer number (16731767700).

Almost surely, 2^66555253561 is an apocalyptic number.

It is an amenable number.

66555253561 is a deficient number, since it is larger than the sum of its proper divisors (371817239).

66555253561 is a wasteful number, since it uses less digits than its factorization.

66555253561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 371817238.

The product of its digits is 4050000, while the sum is 49.

The spelling of 66555253561 in words is "sixty-six billion, five hundred fifty-five million, two hundred fifty-three thousand, five hundred sixty-one".