665353552021 has 4 divisors (see below), whose sum is σ = 683336080492. Its totient is φ = 647371023552.

The previous prime is 665353551983. The next prime is 665353552033. The reversal of 665353552021 is 120255353566.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 581970636900 + 83382915121 = 762870^2 + 288761^2 .

It is a cyclic number.

It is not a de Polignac number, because 665353552021 - 2²¹ = 665351454869 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665353552321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8991264180 + ... + 8991264253.

It is an arithmetic number, because the mean of its divisors is an integer number (170834020123).

Almost surely, 2^665353552021 is an apocalyptic number.

It is an amenable number.

665353552021 is a deficient number, since it is larger than the sum of its proper divisors (17982528471).

665353552021 is a wasteful number, since it uses less digits than its factorization.

665353552021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17982528470.

The product of its (nonzero) digits is 810000, while the sum is 43.

The spelling of 665353552021 in words is "six hundred sixty-five billion, three hundred fifty-three million, five hundred fifty-two thousand, twenty-one".