691568641 has 4 divisors (see below), whose sum is σ = 692512852. Its totient is φ = 690624432.

The previous prime is 691568609. The next prime is 691568663. The reversal of 691568641 is 146865196.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 472410225 + 219158416 = 21735^2 + 14804^2 .

It is a cyclic number.

It is not a de Polignac number, because 691568641 - 2⁵ = 691568609 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 691568591 and 691568600.

It is not an unprimeable number, because it can be changed into a prime (691568681) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 471006 + ... + 472471.

It is an arithmetic number, because the mean of its divisors is an integer number (173128213).

It is a Proth number, since it is equal to 21105 ⋅ 2¹⁵ + 1 and 21105 < 2¹⁵.

Almost surely, 2^691568641 is an apocalyptic number.

It is an amenable number.

691568641 is a deficient number, since it is larger than the sum of its proper divisors (944211).

691568641 is an equidigital number, since it uses as much as digits as its factorization.

691568641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 944210.

The product of its digits is 311040, while the sum is 46.

The square root of 691568641 is about 26297.6926934665. The cubic root of 691568641 is about 884.3247175081.

The spelling of 691568641 in words is "six hundred ninety-one million, five hundred sixty-eight thousand, six hundred forty-one".