691686864 has 180 divisors, whose sum is σ = 2196511200. Its totient is φ = 209252160.

The previous prime is 691686817. The next prime is 691686881. The reversal of 691686864 is 468686196.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a nude number because it is divisible by every one of its digits.

It is a self number, because there is not a number n which added to its sum of digits gives 691686864.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1154437 + ... + 1155035.

It is an arithmetic number, because the mean of its divisors is an integer number (12202840).

Almost surely, 2^691686864 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 691686864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1098255600).

691686864 is an abundant number, since it is smaller than the sum of its proper divisors (1504824336).

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

691686864 is an equidigital number, since it uses as much as digits as its factorization.

691686864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 642 (or 615 counting only the distinct ones).

The product of its digits is 2985984, while the sum is 54.

The square root of 691686864 is about 26299.9403801606. The cubic root of 691686864 is about 884.3751061261.

The spelling of 691686864 in words is "six hundred ninety-one million, six hundred eighty-six thousand, eight hundred sixty-four".