634991 has 6 divisors (see below), whose sum is σ = 738720. Its totient is φ = 544236.

The previous prime is 634979. The next prime is 635003. The reversal of 634991 is 199436.

It is an interprime number because it is at equal distance from previous prime (634979) and next prime (635003).

It is not a de Polignac number, because 634991 - 2⁶ = 634927 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (634901) 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 5 ways as a sum of consecutive naturals, for example, 6431 + ... + 6528.

It is an arithmetic number, because the mean of its divisors is an integer number (123120).

2⁶³⁴⁹⁹¹ is an apocalyptic number.

634991 is a deficient number, since it is larger than the sum of its proper divisors (103729).

634991 is a wasteful number, since it uses less digits than its factorization.

634991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12973 (or 12966 counting only the distinct ones).

The product of its digits is 5832, while the sum is 32.

The square root of 634991 is about 796.8632254032. The cubic root of 634991 is about 85.9519742672.

The spelling of 634991 in words is "six hundred thirty-four thousand, nine hundred ninety-one".