665821155 has 16 divisors (see below), whose sum is σ = 1065647520. Its totient is φ = 354993408.

The previous prime is 665821127. The next prime is 665821157. The reversal of 665821155 is 551128566.

It is not a de Polignac number, because 665821155 - 2¹⁰ = 665820131 is a prime.

It is not an unprimeable number, because it can be changed into a prime (665821157) 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, 70069 + ... + 79001.

It is an arithmetic number, because the mean of its divisors is an integer number (66602970).

Almost surely, 2^665821155 is an apocalyptic number.

665821155 is a deficient number, since it is larger than the sum of its proper divisors (399826365).

665821155 is a wasteful number, since it uses less digits than its factorization.

665821155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13910.

The product of its digits is 72000, while the sum is 39.

The square root of 665821155 is about 25803.5105169820. The cubic root of 665821155 is about 873.2109972604.

The spelling of 665821155 in words is "six hundred sixty-five million, eight hundred twenty-one thousand, one hundred fifty-five".