1565661 has 4 divisors (see below), whose sum is σ = 2087552. Its totient is φ = 1043772.

The previous prime is 1565659. The next prime is 1565671. The reversal of 1565661 is 1665651.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 1565661 - 2¹ = 1565659 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1565611) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 260941 + ... + 260946.

It is an arithmetic number, because the mean of its divisors is an integer number (521888).

2^1565661 is an apocalyptic number.

It is an amenable number.

1565661 is a deficient number, since it is larger than the sum of its proper divisors (521891).

1565661 is an equidigital number, since it uses as much as digits as its factorization.

1565661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 521890.

The product of its digits is 5400, while the sum is 30.

The square root of 1565661 is about 1251.2637611631. The cubic root of 1565661 is about 116.1179191302.

Subtracting from 1565661 its product of digits (5400), we obtain a triangular number (1560261 = T₁₇₆₆).

The spelling of 1565661 in words is "one million, five hundred sixty-five thousand, six hundred sixty-one".