66561561494 has 16 divisors (see below), whose sum is σ = 100572239040. Its totient is φ = 33037959240.

The previous prime is 66561561431. The next prime is 66561561497. The reversal of 66561561494 is 49416516566.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66561561497) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 161189 + ... + 398879.

It is an arithmetic number, because the mean of its divisors is an integer number (6285764940).

Almost surely, 2^66561561494 is an apocalyptic number.

66561561494 is a deficient number, since it is larger than the sum of its proper divisors (34010677546).

66561561494 is a wasteful number, since it uses less digits than its factorization.

66561561494 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 238715.

The product of its digits is 4665600, while the sum is 53.

The spelling of 66561561494 in words is "sixty-six billion, five hundred sixty-one million, five hundred sixty-one thousand, four hundred ninety-four".