661379566105 has 4 divisors (see below), whose sum is σ = 793655479332. Its totient is φ = 529103652880.

The previous prime is 661379566097. The next prime is 661379566117. The reversal of 661379566105 is 501665973166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 501665973166 = 2 ⋅250832986583.

It can be written as a sum of positive squares in 2 ways, for example, as 77218961689 + 584160604416 = 277883^2 + 764304^2 .

It is not a de Polignac number, because 661379566105 - 2³ = 661379566097 is a prime.

It is a super-2 number, since 2×661379566105² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66137956606 + ... + 66137956615.

It is an arithmetic number, because the mean of its divisors is an integer number (198413869833).

Almost surely, 2^661379566105 is an apocalyptic number.

It is an amenable number.

661379566105 is a deficient number, since it is larger than the sum of its proper divisors (132275913227).

661379566105 is a wasteful number, since it uses less digits than its factorization.

661379566105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132275913226.

The product of its (nonzero) digits is 6123600, while the sum is 55.

The spelling of 661379566105 in words is "six hundred sixty-one billion, three hundred seventy-nine million, five hundred sixty-six thousand, one hundred five".