66561561501 has 16 divisors (see below), whose sum is σ = 93903791040. Its totient is φ = 41821056000.

The previous prime is 66561561499. The next prime is 66561561509. The reversal of 66561561501 is 10516516566.

It is not a de Polignac number, because 66561561501 - 2¹ = 66561561499 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66561561509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3014250 + ... + 3036251.

It is an arithmetic number, because the mean of its divisors is an integer number (5868986940).

Almost surely, 2^66561561501 is an apocalyptic number.

It is an amenable number.

66561561501 is a deficient number, since it is larger than the sum of its proper divisors (27342229539).

66561561501 is a wasteful number, since it uses less digits than its factorization.

66561561501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6050716.

The product of its (nonzero) digits is 162000, while the sum is 42.

The spelling of 66561561501 in words is "sixty-six billion, five hundred sixty-one million, five hundred sixty-one thousand, five hundred one".