691791840 has 216 divisors, whose sum is σ = 2455132680. Its totient is φ = 184197888.

The previous prime is 691791799. The next prime is 691791847. The reversal of 691791840 is 48197196.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (216).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691791847) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1049431 + ... + 1050089.

It is an arithmetic number, because the mean of its divisors is an integer number (11366355).

Almost surely, 2^691791840 is an apocalyptic number.

691791840 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 691791840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1227566340).

691791840 is an abundant number, since it is smaller than the sum of its proper divisors (1763340840).

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

691791840 is an frugal number, since it uses more digits than its factorization.

691791840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 698 (or 669 counting only the distinct ones).

The product of its (nonzero) digits is 108864, while the sum is 45.

The square root of 691791840 is about 26301.9360504127. The cubic root of 691791840 is about 884.4198438389.

The spelling of 691791840 in words is "six hundred ninety-one million, seven hundred ninety-one thousand, eight hundred forty".