691171993 has 8 divisors (see below), whose sum is σ = 728497800. Its totient is φ = 654745728.

The previous prime is 691171991. The next prime is 691172003. The reversal of 691171993 is 399171196.

It can be written as a sum of positive squares in 4 ways, for example, as 116467264 + 574704729 = 10792^2 + 23973^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 691171993 - 2¹ = 691171991 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (691171991) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 223308 + ... + 226381.

It is an arithmetic number, because the mean of its divisors is an integer number (91062225).

Almost surely, 2^691171993 is an apocalyptic number.

It is an amenable number.

691171993 is a deficient number, since it is larger than the sum of its proper divisors (37325807).

691171993 is a wasteful number, since it uses less digits than its factorization.

691171993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 449771.

The product of its digits is 91854, while the sum is 46.

The square root of 691171993 is about 26290.1501136833. The cubic root of 691171993 is about 884.1556175367.

The spelling of 691171993 in words is "six hundred ninety-one million, one hundred seventy-one thousand, nine hundred ninety-three".