661768 has 8 divisors (see below), whose sum is σ = 1240830. Its totient is φ = 330880.

The previous prime is 661741. The next prime is 661769. The reversal of 661768 is 867166.

It can be written as a sum of positive squares in only one way, i.e., 636804 + 24964 = 798^2 + 158^2 .

It is a tau number, because it is divible by the number of its divisors (8).

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

661768 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 41353 + ... + 41368.

2⁶⁶¹⁷⁶⁸ is an apocalyptic number.

It is an amenable number.

661768 is a deficient number, since it is larger than the sum of its proper divisors (579062).

661768 is a wasteful number, since it uses less digits than its factorization.

661768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 82727 (or 82723 counting only the distinct ones).

The product of its digits is 12096, while the sum is 34.

The square root of 661768 is about 813.4912415017. The cubic root of 661768 is about 87.1435512672.

The spelling of 661768 in words is "six hundred sixty-one thousand, seven hundred sixty-eight".