661261616807 has 16 divisors (see below), whose sum is σ = 744936238080. Its totient is φ = 581528740800.

The previous prime is 661261616707. The next prime is 661261616809. The reversal of 661261616807 is 708616162166.

It is a cyclic number.

It is not a de Polignac number, because 661261616807 - 2²⁰ = 661260568231 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661261616809) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 503483 + ... + 1255395.

It is an arithmetic number, because the mean of its divisors is an integer number (46558514880).

Almost surely, 2^661261616807 is an apocalyptic number.

661261616807 is a deficient number, since it is larger than the sum of its proper divisors (83674621273).

661261616807 is a wasteful number, since it uses less digits than its factorization.

661261616807 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 754534.

The product of its (nonzero) digits is 870912, while the sum is 50.

The spelling of 661261616807 in words is "six hundred sixty-one billion, two hundred sixty-one million, six hundred sixteen thousand, eight hundred seven".