2191639 has 4 divisors (see below), whose sum is σ = 2209024. Its totient is φ = 2174256.

The previous prime is 2191633. The next prime is 2191687. The reversal of 2191639 is 9361912.

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 2191639 - 2⁹ = 2191127 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 2191639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2191633) 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, 8502 + ... + 8755.

It is an arithmetic number, because the mean of its divisors is an integer number (552256).

2^2191639 is an apocalyptic number.

2191639 is a deficient number, since it is larger than the sum of its proper divisors (17385).

2191639 is a wasteful number, since it uses less digits than its factorization.

2191639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17384.

The product of its digits is 2916, while the sum is 31.

The square root of 2191639 is about 1480.4185219052. The cubic root of 2191639 is about 129.8941742315.

The spelling of 2191639 in words is "two million, one hundred ninety-one thousand, six hundred thirty-nine".