691281864 has 320 divisors, whose sum is σ = 2512540800. Its totient is φ = 172440576.

The previous prime is 691281847. The next prime is 691281869. The reversal of 691281864 is 468182196.

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

It is not an unprimeable number, because it can be changed into a prime (691281869) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 1120084 + ... + 1120700.

It is an arithmetic number, because the mean of its divisors is an integer number (7851690).

Almost surely, 2^691281864 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 691281864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1256270400).

691281864 is an abundant number, since it is smaller than the sum of its proper divisors (1821258936).

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

691281864 is a wasteful number, since it uses less digits than its factorization.

691281864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 674 (or 661 counting only the distinct ones).

The product of its digits is 165888, while the sum is 45.

The square root of 691281864 is about 26292.2396155215. The cubic root of 691281864 is about 884.2024644942.

The spelling of 691281864 in words is "six hundred ninety-one million, two hundred eighty-one thousand, eight hundred sixty-four".