501565661 has 4 divisors (see below), whose sum is σ = 504336924. Its totient is φ = 498794400.

The previous prime is 501565657. The next prime is 501565679. The reversal of 501565661 is 166565105.

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 30415225 + 471150436 = 5515^2 + 21706^2 .

It is a cyclic number.

It is not a de Polignac number, because 501565661 - 2² = 501565657 is a prime.

It is a super-2 number, since 2×501565661² = 503136224588733842, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (501565601) 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, 1385360 + ... + 1385721.

It is an arithmetic number, because the mean of its divisors is an integer number (126084231).

Almost surely, 2^501565661 is an apocalyptic number.

It is an amenable number.

501565661 is a deficient number, since it is larger than the sum of its proper divisors (2771263).

501565661 is a wasteful number, since it uses less digits than its factorization.

501565661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2771262.

The product of its (nonzero) digits is 27000, while the sum is 35.

The square root of 501565661 is about 22395.6616557761. The cubic root of 501565661 is about 794.5281067498.

The spelling of 501565661 in words is "five hundred one million, five hundred sixty-five thousand, six hundred sixty-one".