1661761 has 4 divisors (see below), whose sum is σ = 1671124. Its totient is φ = 1652400.

The previous prime is 1661741. The next prime is 1661789. The reversal of 1661761 is 1671661.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 409600 + 1252161 = 640^2 + 1119^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661761 - 2⁹ = 1661249 is a prime.

It is a super-2 number, since 2×1661761² = 5522899242242, which contains 22 as substring.

It is a Duffinian number.

1661761 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (1661731) 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, 4410 + ... + 4771.

It is an arithmetic number, because the mean of its divisors is an integer number (417781).

2^1661761 is an apocalyptic number.

1661761 is the 577-th centered decagonal number.

It is an amenable number.

1661761 is a deficient number, since it is larger than the sum of its proper divisors (9363).

1661761 is an equidigital number, since it uses as much as digits as its factorization.

1661761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9362.

The product of its digits is 1512, while the sum is 28.

The square root of 1661761 is about 1289.0930920612. The cubic root of 1661761 is about 118.4466696117.

The spelling of 1661761 in words is "one million, six hundred sixty-one thousand, seven hundred sixty-one".