691081 has 4 divisors (see below), whose sum is σ = 721152. Its totient is φ = 661012.

The previous prime is 691079. The next prime is 691109. The reversal of 691081 is 180196.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 691081 - 2¹ = 691079 is a prime.

It is a super-2 number, since 2×691081² = 955185897122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (691001) 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, 15001 + ... + 15046.

It is an arithmetic number, because the mean of its divisors is an integer number (180288).

2⁶⁹¹⁰⁸¹ is an apocalyptic number.

It is an amenable number.

691081 is a deficient number, since it is larger than the sum of its proper divisors (30071).

691081 is a wasteful number, since it uses less digits than its factorization.

691081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30070.

The product of its (nonzero) digits is 432, while the sum is 25.

The square root of 691081 is about 831.3128171753. The cubic root of 691081 is about 88.4116816050.

The spelling of 691081 in words is "six hundred ninety-one thousand, eighty-one".