66561561507 has 32 divisors (see below), whose sum is σ = 109419766272. Its totient is φ = 35122374144.

The previous prime is 66561561499. The next prime is 66561561509. The reversal of 66561561507 is 70516516566.

It is not a de Polignac number, because 66561561507 - 2³ = 66561561499 is a prime.

It is a super-2 number, since 2×66561561507² (a number of 22 digits) contains 22 as substring.

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

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1740013 + ... + 1777854.

It is an arithmetic number, because the mean of its divisors is an integer number (3419367696).

Almost surely, 2^66561561507 is an apocalyptic number.

66561561507 is a deficient number, since it is larger than the sum of its proper divisors (42858204765).

66561561507 is a wasteful number, since it uses less digits than its factorization.

66561561507 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3517947.

The product of its (nonzero) digits is 1134000, while the sum is 48.

The spelling of 66561561507 in words is "sixty-six billion, five hundred sixty-one million, five hundred sixty-one thousand, five hundred seven".