661506005 has 4 divisors (see below), whose sum is σ = 793807212. Its totient is φ = 529204800.

The previous prime is 661505987. The next prime is 661506029. The reversal of 661506005 is 500605166.

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 408282436 + 253223569 = 20206^2 + 15913^2 .

It is not a de Polignac number, because 661506005 - 2¹⁶ = 661440469 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66150596 + ... + 66150605.

It is an arithmetic number, because the mean of its divisors is an integer number (198451803).

Almost surely, 2^661506005 is an apocalyptic number.

It is an amenable number.

661506005 is a deficient number, since it is larger than the sum of its proper divisors (132301207).

661506005 is a wasteful number, since it uses less digits than its factorization.

661506005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132301206.

The product of its (nonzero) digits is 5400, while the sum is 29.

The square root of 661506005 is about 25719.7590385291. The cubic root of 661506005 is about 871.3204965918.

The spelling of 661506005 in words is "six hundred sixty-one million, five hundred six thousand, five".