661040 has 20 divisors (see below), whose sum is σ = 1537104. Its totient is φ = 264384.

The previous prime is 661027. The next prime is 661049. The reversal of 661040 is 40166.

It is a tau number, because it is divible by the number of its divisors (20).

It is not an unprimeable number, because it can be changed into a prime (661049) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4052 + ... + 4211.

2⁶⁶¹⁰⁴⁰ is an apocalyptic number.

It is an amenable number.

661040 is an abundant number, since it is smaller than the sum of its proper divisors (876064).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

661040 is a wasteful number, since it uses less digits than its factorization.

661040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8276 (or 8270 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 17.

The square root of 661040 is about 813.0436642641. The cubic root of 661040 is about 87.1115844838. Note that the first 3 decimals are identical.

The spelling of 661040 in words is "six hundred sixty-one thousand, forty".