661597 has 4 divisors (see below), whose sum is σ = 679516. Its totient is φ = 643680.

The previous prime is 661553. The next prime is 661603. The reversal of 661597 is 795166.

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 436921 + 224676 = 661^2 + 474^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-661597 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 (661517) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8904 + ... + 8977.

It is an arithmetic number, because the mean of its divisors is an integer number (169879).

2⁶⁶¹⁵⁹⁷ is an apocalyptic number.

It is an amenable number.

661597 is a deficient number, since it is larger than the sum of its proper divisors (17919).

661597 is a wasteful number, since it uses less digits than its factorization.

661597 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17918.

The product of its digits is 11340, while the sum is 34.

The square root of 661597 is about 813.3861321660. The cubic root of 661597 is about 87.1360446934.

It can be divided in two parts, 66159 and 7, that added together give a palindrome (66166).

The spelling of 661597 in words is "six hundred sixty-one thousand, five hundred ninety-seven".