661116266501 has 4 divisors (see below), whose sum is σ = 661358525100. Its totient is φ = 660874007904.

The previous prime is 661116266497. The next prime is 661116266519. The reversal of 661116266501 is 105662611166.

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

It can be written as a sum of positive squares in 2 ways, for example, as 467788970401 + 193327296100 = 683951^2 + 439690^2 .

It is a cyclic number.

It is not a de Polignac number, because 661116266501 - 2² = 661116266497 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661116266561) 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, 121125206 + ... + 121130663.

It is an arithmetic number, because the mean of its divisors is an integer number (165339631275).

Almost surely, 2^661116266501 is an apocalyptic number.

It is an amenable number.

661116266501 is a deficient number, since it is larger than the sum of its proper divisors (242258599).

661116266501 is a wasteful number, since it uses less digits than its factorization.

661116266501 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 242258598.

The product of its (nonzero) digits is 77760, while the sum is 41.

Adding to 661116266501 its reverse (105662611166), we get a palindrome (766778877667).

The spelling of 661116266501 in words is "six hundred sixty-one billion, one hundred sixteen million, two hundred sixty-six thousand, five hundred one".