2158661 has 4 divisors (see below), whose sum is σ = 2166732. Its totient is φ = 2150592.

The previous prime is 2158649. The next prime is 2158679. The reversal of 2158661 is 1668512.

It is a happy number.

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 1366561 + 792100 = 1169^2 + 890^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2158661 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2158601) 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, 3620 + ... + 4173.

It is an arithmetic number, because the mean of its divisors is an integer number (541683).

2^2158661 is an apocalyptic number.

It is an amenable number.

2158661 is a deficient number, since it is larger than the sum of its proper divisors (8071).

2158661 is an equidigital number, since it uses as much as digits as its factorization.

2158661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8070.

The product of its digits is 2880, while the sum is 29.

The square root of 2158661 is about 1469.2382379995. The cubic root of 2158661 is about 129.2393648801.

The spelling of 2158661 in words is "two million, one hundred fifty-eight thousand, six hundred sixty-one".