661505 has 8 divisors (see below), whose sum is σ = 854952. Its totient is φ = 488448.

The previous prime is 661483. The next prime is 661513. The reversal of 661505 is 505166.

It can be written as a sum of positive squares in 4 ways, for example, as 27889 + 633616 = 167^2 + 796^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661505 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5024 + ... + 5153.

It is an arithmetic number, because the mean of its divisors is an integer number (106869).

It is a Proth number, since it is equal to 323 ⋅ 2¹¹ + 1 and 323 < 2¹¹.

2⁶⁶¹⁵⁰⁵ is an apocalyptic number.

661505 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

661505 is a deficient number, since it is larger than the sum of its proper divisors (193447).

661505 is a wasteful number, since it uses less digits than its factorization.

661505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10195.

The product of its (nonzero) digits is 900, while the sum is 23.

The square root of 661505 is about 813.3295764941. The cubic root of 661505 is about 87.1320055337.

The spelling of 661505 in words is "six hundred sixty-one thousand, five hundred five".