661761 has 6 divisors (see below), whose sum is σ = 955890. Its totient is φ = 441168.

The previous prime is 661741. The next prime is 661769. The reversal of 661761 is 167166.

It can be written as a sum of positive squares in only one way, i.e., 608400 + 53361 = 780^2 + 231^2 .

It is not a de Polignac number, because 661761 - 2⁶ = 661697 is a prime.

It is a super-2 number, since 2×661761² = 875855242242, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (661769) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 36756 + ... + 36773.

It is an arithmetic number, because the mean of its divisors is an integer number (159315).

2⁶⁶¹⁷⁶¹ is an apocalyptic number.

It is an amenable number.

661761 is a deficient number, since it is larger than the sum of its proper divisors (294129).

661761 is a wasteful number, since it uses less digits than its factorization.

661761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 73535 (or 73532 counting only the distinct ones).

The product of its digits is 1512, while the sum is 27.

The square root of 661761 is about 813.4869390470. The cubic root of 661761 is about 87.1432440059.

The spelling of 661761 in words is "six hundred sixty-one thousand, seven hundred sixty-one".