66561561502 has 4 divisors (see below), whose sum is σ = 99842342256. Its totient is φ = 33280780750.

The previous prime is 66561561499. The next prime is 66561561509. The reversal of 66561561502 is 20516516566.

It is a semiprime because it is the product of two primes.

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 as a sum of consecutive naturals, namely, 16640390374 + ... + 16640390377.

It is an arithmetic number, because the mean of its divisors is an integer number (24960585564).

Almost surely, 2^66561561502 is an apocalyptic number.

66561561502 is a deficient number, since it is larger than the sum of its proper divisors (33280780754).

66561561502 is a wasteful number, since it uses less digits than its factorization.

66561561502 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33280780753.

The product of its (nonzero) digits is 324000, while the sum is 43.

The spelling of 66561561502 in words is "sixty-six billion, five hundred sixty-one million, five hundred sixty-one thousand, five hundred two".