2156691 has 4 divisors (see below), whose sum is σ = 2875592. Its totient is φ = 1437792.

The previous prime is 2156683. The next prime is 2156699. The reversal of 2156691 is 1966512.

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

It is an interprime number because it is at equal distance from previous prime (2156683) and next prime (2156699).

It is not a de Polignac number, because 2156691 - 2³ = 2156683 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2156699) 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, 359446 + ... + 359451.

It is an arithmetic number, because the mean of its divisors is an integer number (718898).

2^2156691 is an apocalyptic number.

2156691 is a deficient number, since it is larger than the sum of its proper divisors (718901).

2156691 is an equidigital number, since it uses as much as digits as its factorization.

2156691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 718900.

The product of its digits is 3240, while the sum is 30.

The square root of 2156691 is about 1468.5676695338. The cubic root of 2156691 is about 129.2000381805.

The spelling of 2156691 in words is "two million, one hundred fifty-six thousand, six hundred ninety-one".