665686711537 has 4 divisors (see below), whose sum is σ = 681922972836. Its totient is φ = 649450450240.

The previous prime is 665686711517. The next prime is 665686711541. The reversal of 665686711537 is 735117686566.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 735117686566 = 2 ⋅367558843283.

It can be written as a sum of positive squares in 2 ways, for example, as 44149994161 + 621536717376 = 210119^2 + 788376^2 .

It is a cyclic number.

It is not a de Polignac number, because 665686711537 - 2³⁵ = 631326973169 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (665686711517) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8118130588 + ... + 8118130669.

It is an arithmetic number, because the mean of its divisors is an integer number (170480743209).

Almost surely, 2^665686711537 is an apocalyptic number.

It is an amenable number.

665686711537 is a deficient number, since it is larger than the sum of its proper divisors (16236261299).

665686711537 is a wasteful number, since it uses less digits than its factorization.

665686711537 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16236261298.

The product of its digits is 38102400, while the sum is 61.

The spelling of 665686711537 in words is "six hundred sixty-five billion, six hundred eighty-six million, seven hundred eleven thousand, five hundred thirty-seven".