691643855 has 16 divisors (see below), whose sum is σ = 949030464. Its totient is φ = 474024960.

The previous prime is 691643851. The next prime is 691643857. The reversal of 691643855 is 558346196.

It is a happy number.

It is not a de Polignac number, because 691643855 - 2² = 691643851 is a prime.

It is a super-2 number, since 2×691643855² = 956742444318522050, which contains 22 as substring.

It is a Smith number, since the sum of its digits (47) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691643851) 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 15 ways as a sum of consecutive naturals, for example, 86945 + ... + 94565.

It is an arithmetic number, because the mean of its divisors is an integer number (59314404).

Almost surely, 2^691643855 is an apocalyptic number.

691643855 is a deficient number, since it is larger than the sum of its proper divisors (257386609).

691643855 is a wasteful number, since it uses less digits than its factorization.

691643855 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10226.

The product of its digits is 777600, while the sum is 47.

The square root of 691643855 is about 26299.1227039991. The cubic root of 691643855 is about 884.3567756361.

The spelling of 691643855 in words is "six hundred ninety-one million, six hundred forty-three thousand, eight hundred fifty-five".