661145 has 4 divisors (see below), whose sum is σ = 793380. Its totient is φ = 528912.

The previous prime is 661139. The next prime is 661183. The reversal of 661145 is 541166.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 541166 = 2 ⋅270583.

It can be written as a sum of positive squares in 2 ways, for example, as 169744 + 491401 = 412^2 + 701^2 .

It is a cyclic number.

It is not a de Polignac number, because 661145 - 2¹² = 657049 is a prime.

It is a super-2 number, since 2×661145² = 874225422050, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 661145.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 66110 + ... + 66119.

It is an arithmetic number, because the mean of its divisors is an integer number (198345).

2⁶⁶¹¹⁴⁵ is an apocalyptic number.

It is an amenable number.

661145 is a deficient number, since it is larger than the sum of its proper divisors (132235).

661145 is a wasteful number, since it uses less digits than its factorization.

661145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 132234.

The product of its digits is 720, while the sum is 23.

The square root of 661145 is about 813.1082338779. The cubic root of 661145 is about 87.1161965255.

The spelling of 661145 in words is "six hundred sixty-one thousand, one hundred forty-five".