991649 has 4 divisors (see below), whose sum is σ = 995460. Its totient is φ = 987840.

The previous prime is 991643. The next prime is 991651. The reversal of 991649 is 946199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 946199 = 313 ⋅3023.

It can be written as a sum of positive squares in 2 ways, for example, as 351649 + 640000 = 593^2 + 800^2 .

It is a cyclic number.

It is not a de Polignac number, because 991649 - 2⁴ = 991633 is a prime.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991649.

It is not an unprimeable number, because it can be changed into a prime (991643) 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, 1484 + ... + 2045.

It is an arithmetic number, because the mean of its divisors is an integer number (248865).

2⁹⁹¹⁶⁴⁹ is an apocalyptic number.

It is an amenable number.

991649 is a deficient number, since it is larger than the sum of its proper divisors (3811).

991649 is a wasteful number, since it uses less digits than its factorization.

991649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3810.

The product of its digits is 17496, while the sum is 38.

The square root of 991649 is about 995.8157460093. The cubic root of 991649 is about 99.7208548382.

The spelling of 991649 in words is "nine hundred ninety-one thousand, six hundred forty-nine".