4991991 has 4 divisors (see below), whose sum is σ = 6655992. Its totient is φ = 3327992.

The previous prime is 4991983. The next prime is 4992007. The reversal of 4991991 is 1991994.

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 4991991 - 2³ = 4991983 is a prime.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (4991951) 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, 831996 + ... + 832001.

It is an arithmetic number, because the mean of its divisors is an integer number (1663998).

Almost surely, 2^4991991 is an apocalyptic number.

4991991 is a deficient number, since it is larger than the sum of its proper divisors (1664001).

4991991 is a wasteful number, since it uses less digits than its factorization.

4991991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1664000.

The product of its digits is 26244, while the sum is 42.

The square root of 4991991 is about 2234.2763929290. The cubic root of 4991991 is about 170.9062445597.

The spelling of 4991991 in words is "four million, nine hundred ninety-one thousand, nine hundred ninety-one".