691440 has 80 divisors (see below), whose sum is σ = 2226048. Its totient is φ = 177408.

The previous prime is 691433. The next prime is 691451. The reversal of 691440 is 44196.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 691440.

It is a congruent number.

It is an unprimeable number.

691440 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10287 + ... + 10353.

2⁶⁹¹⁴⁴⁰ is an apocalyptic number.

691440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 691440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1113024).

691440 is an abundant number, since it is smaller than the sum of its proper divisors (1534608).

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

691440 is a wasteful number, since it uses less digits than its factorization.

691440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 126 (or 120 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 24.

The square root of 691440 is about 831.5287126732. The cubic root of 691440 is about 88.4269882040.

The spelling of 691440 in words is "six hundred ninety-one thousand, four hundred forty".