2640991 has 4 divisors (see below), whose sum is σ = 2646000. Its totient is φ = 2635984.

The previous prime is 2640973. The next prime is 2640997. The reversal of 2640991 is 1990462.

It is a happy number.

2640991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 2640991 - 2⁵ = 2640959 is a prime.

It is a Duffinian number.

2640991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2640997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1606 + ... + 2803.

It is an arithmetic number, because the mean of its divisors is an integer number (661500).

2^2640991 is an apocalyptic number.

2640991 is a deficient number, since it is larger than the sum of its proper divisors (5009).

2640991 is an equidigital number, since it uses as much as digits as its factorization.

2640991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5008.

The product of its (nonzero) digits is 3888, while the sum is 31.

The square root of 2640991 is about 1625.1126114827. The cubic root of 2640991 is about 138.2257559454.

The spelling of 2640991 in words is "two million, six hundred forty thousand, nine hundred ninety-one".