661568 has 14 divisors (see below), whose sum is σ = 1312926. Its totient is φ = 330752.

The previous prime is 661553. The next prime is 661603. The reversal of 661568 is 865166.

It can be written as a sum of positive squares in only one way, i.e., 399424 + 262144 = 632^2 + 512^2 .

It is a Harshad number since it is a multiple of its sum of digits (32).

It is an Ulam number.

It is a congruent number.

It is an unprimeable number.

661568 is an untouchable number, because it is not equal to the sum of proper divisors of any 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 as a sum of consecutive naturals, namely, 5105 + ... + 5232.

2⁶⁶¹⁵⁶⁸ is an apocalyptic number.

It is an amenable number.

661568 is a deficient number, since it is larger than the sum of its proper divisors (651358).

661568 is a wasteful number, since it uses less digits than its factorization.

661568 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10349 (or 10339 counting only the distinct ones).

The product of its digits is 8640, while the sum is 32.

The square root of 661568 is about 813.3683052591. The cubic root of 661568 is about 87.1347715204.

The spelling of 661568 in words is "six hundred sixty-one thousand, five hundred sixty-eight".