665551655 has 4 divisors (see below), whose sum is σ = 798661992. Its totient is φ = 532441320.

The previous prime is 665551651. The next prime is 665551673. The reversal of 665551655 is 556155566.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 556155566 = 2 ⋅278077783.

It is not a de Polignac number, because 665551655 - 2² = 665551651 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 (665551651) 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, 66555161 + ... + 66555170.

It is an arithmetic number, because the mean of its divisors is an integer number (199665498).

Almost surely, 2^665551655 is an apocalyptic number.

665551655 is a deficient number, since it is larger than the sum of its proper divisors (133110337).

665551655 is a wasteful number, since it uses less digits than its factorization.

665551655 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133110336.

The product of its digits is 675000, while the sum is 44.

The square root of 665551655 is about 25798.2878307844. The cubic root of 665551655 is about 873.0931667588.

The spelling of 665551655 in words is "six hundred sixty-five million, five hundred fifty-one thousand, six hundred fifty-five".