691638 has 16 divisors (see below), whose sum is σ = 1456320. Its totient is φ = 218376.

The previous prime is 691637. The next prime is 691651. The reversal of 691638 is 836196.

It is a junction number, because it is equal to n+sod(n) for n = 691599 and 691608.

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 691638.

It is not an unprimeable number, because it can be changed into a prime (691631) 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 7 ways as a sum of consecutive naturals, for example, 2920 + ... + 3147.

It is an arithmetic number, because the mean of its divisors is an integer number (91020).

2⁶⁹¹⁶³⁸ is an apocalyptic number.

691638 is an abundant number, since it is smaller than the sum of its proper divisors (764682).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

691638 is a wasteful number, since it uses less digits than its factorization.

691638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6091.

The product of its digits is 7776, while the sum is 33.

The square root of 691638 is about 831.6477619762. The cubic root of 691638 is about 88.4354280169.

The spelling of 691638 in words is "six hundred ninety-one thousand, six hundred thirty-eight".