991631 has 4 divisors (see below), whose sum is σ = 1001952. Its totient is φ = 981312.

The previous prime is 991621. The next prime is 991633. The reversal of 991631 is 136199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 136199 = 7 ⋅19457.

It is a cyclic number.

It is not a de Polignac number, because 991631 - 2⁶ = 991567 is a prime.

It is a super-2 number, since 2×991631² = 1966664080322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 991594 and 991603.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991631.

It is not an unprimeable number, because it can be changed into a prime (991633) 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, 5015 + ... + 5208.

It is an arithmetic number, because the mean of its divisors is an integer number (250488).

2⁹⁹¹⁶³¹ is an apocalyptic number.

991631 is a deficient number, since it is larger than the sum of its proper divisors (10321).

991631 is a wasteful number, since it uses less digits than its factorization.

991631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10320.

The product of its digits is 1458, while the sum is 29.

The square root of 991631 is about 995.8067081517. The cubic root of 991631 is about 99.7202514707.

The spelling of 991631 in words is "nine hundred ninety-one thousand, six hundred thirty-one".