661757 has 4 divisors (see below), whose sum is σ = 683136. Its totient is φ = 640380.

The previous prime is 661741. The next prime is 661769. The reversal of 661757 is 757166.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 757166 = 2 ⋅378583.

It is a cyclic number.

It is not a de Polignac number, because 661757 - 2⁴ = 661741 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 (661777) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10643 + ... + 10704.

It is an arithmetic number, because the mean of its divisors is an integer number (170784).

2⁶⁶¹⁷⁵⁷ is an apocalyptic number.

It is an amenable number.

661757 is a deficient number, since it is larger than the sum of its proper divisors (21379).

661757 is a wasteful number, since it uses less digits than its factorization.

661757 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21378.

The product of its digits is 8820, while the sum is 32.

The square root of 661757 is about 813.4844804912. The cubic root of 661757 is about 87.1430684271.

The spelling of 661757 in words is "six hundred sixty-one thousand, seven hundred fifty-seven".