691643 has 4 divisors (see below), whose sum is σ = 693360. Its totient is φ = 689928.

The previous prime is 691637. The next prime is 691651. The reversal of 691643 is 346196.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691643 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 691643.

It is not an unprimeable number, because it can be changed into a prime (691693) 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, 113 + ... + 1181.

It is an arithmetic number, because the mean of its divisors is an integer number (173340).

2⁶⁹¹⁶⁴³ is an apocalyptic number.

691643 is a deficient number, since it is larger than the sum of its proper divisors (1717).

691643 is a wasteful number, since it uses less digits than its factorization.

691643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1716.

The product of its digits is 3888, while the sum is 29.

The square root of 691643 is about 831.6507680511. The cubic root of 691643 is about 88.4356411226.

The spelling of 691643 in words is "six hundred ninety-one thousand, six hundred forty-three".