1661365 has 4 divisors (see below), whose sum is σ = 1993644. Its totient is φ = 1329088.

The previous prime is 1661353. The next prime is 1661431. The reversal of 1661365 is 5631661.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 5631661 = 7 ⋅804523.

It can be written as a sum of positive squares in 2 ways, for example, as 492804 + 1168561 = 702^2 + 1081^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661365 - 2⁵ = 1661333 is a prime.

It is a Duffinian number.

It is a congruent number.

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, 166132 + ... + 166141.

It is an arithmetic number, because the mean of its divisors is an integer number (498411).

2^1661365 is an apocalyptic number.

It is an amenable number.

1661365 is a deficient number, since it is larger than the sum of its proper divisors (332279).

1661365 is an equidigital number, since it uses as much as digits as its factorization.

1661365 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 332278.

The product of its digits is 3240, while the sum is 28.

The square root of 1661365 is about 1288.9394865547. The cubic root of 1661365 is about 118.4372601945.

The spelling of 1661365 in words is "one million, six hundred sixty-one thousand, three hundred sixty-five".