661345 has 8 divisors (see below), whose sum is σ = 821160. Its totient is φ = 510720.

The previous prime is 661343. The next prime is 661361. The reversal of 661345 is 543166.

It can be written as a sum of positive squares in 4 ways, for example, as 40401 + 620944 = 201^2 + 788^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 661345 - 2¹ = 661343 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661343) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2136 + ... + 2425.

It is an arithmetic number, because the mean of its divisors is an integer number (102645).

2⁶⁶¹³⁴⁵ is an apocalyptic number.

It is an amenable number.

661345 is a deficient number, since it is larger than the sum of its proper divisors (159815).

661345 is a wasteful number, since it uses less digits than its factorization.

661345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4595.

The product of its digits is 2160, while the sum is 25.

The square root of 661345 is about 813.2312094355. The cubic root of 661345 is about 87.1249800161.

The spelling of 661345 in words is "six hundred sixty-one thousand, three hundred forty-five".