501566661 has 20 divisors (see below), whose sum is σ = 756141100. Its totient is φ = 331304256.

The previous prime is 501566647. The next prime is 501566669. The reversal of 501566661 is 166665105.

It can be written as a sum of positive squares in 2 ways, for example, as 121550625 + 380016036 = 11025^2 + 19494^2 .

It is not a de Polignac number, because 501566661 - 2¹⁷ = 501435589 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 (501566669) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 19576 + ... + 37233.

It is an arithmetic number, because the mean of its divisors is an integer number (37807055).

Almost surely, 2^501566661 is an apocalyptic number.

It is an amenable number.

501566661 is a deficient number, since it is larger than the sum of its proper divisors (254574439).

501566661 is a wasteful number, since it uses less digits than its factorization.

501566661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56930 (or 56921 counting only the distinct ones).

The product of its (nonzero) digits is 32400, while the sum is 36.

The square root of 501566661 is about 22395.6839815175. The cubic root of 501566661 is about 794.5286347814.

The spelling of 501566661 in words is "five hundred one million, five hundred sixty-six thousand, six hundred sixty-one".