2171987 has 4 divisors (see below), whose sum is σ = 2177856. Its totient is φ = 2166120.

The previous prime is 2171977. The next prime is 2171989. The reversal of 2171987 is 7891712.

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

It is a cyclic number.

It is not a de Polignac number, because 2171987 - 2¹⁴ = 2155603 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2171989) 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, 2339 + ... + 3132.

It is an arithmetic number, because the mean of its divisors is an integer number (544464).

2^2171987 is an apocalyptic number.

2171987 is a deficient number, since it is larger than the sum of its proper divisors (5869).

2171987 is an equidigital number, since it uses as much as digits as its factorization.

2171987 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5868.

The product of its digits is 7056, while the sum is 35.

The square root of 2171987 is about 1473.7662636931. The cubic root of 2171987 is about 129.5047627234.

The spelling of 2171987 in words is "two million, one hundred seventy-one thousand, nine hundred eighty-seven".