691640 has 16 divisors (see below), whose sum is σ = 1556280. Its totient is φ = 276640.

The previous prime is 691637. The next prime is 691651. The reversal of 691640 is 46196.

691640 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8606 + ... + 8685.

2⁶⁹¹⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

691640 is an abundant number, since it is smaller than the sum of its proper divisors (864640).

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

691640 is a wasteful number, since it uses less digits than its factorization.

691640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17302 (or 17298 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 26.

The square root of 691640 is about 831.6489644075. The cubic root of 691640 is about 88.4355132593.

It can be divided in two parts, 691 and 640, that added together give a palindrome (1331).

The spelling of 691640 in words is "six hundred ninety-one thousand, six hundred forty".