978691 has 4 divisors (see below), whose sum is σ = 1118512. Its totient is φ = 838872.

The previous prime is 978689. The next prime is 978697. The reversal of 978691 is 196879.

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

It is a cyclic number.

It is not a de Polignac number, because 978691 - 2¹ = 978689 is a prime.

It is a Duffinian number.

978691 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (978697) 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, 69900 + ... + 69913.

It is an arithmetic number, because the mean of its divisors is an integer number (279628).

2⁹⁷⁸⁶⁹¹ is an apocalyptic number.

978691 is a deficient number, since it is larger than the sum of its proper divisors (139821).

978691 is a wasteful number, since it uses less digits than its factorization.

978691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139820.

The product of its digits is 27216, while the sum is 40.

The square root of 978691 is about 989.2881278980. The cubic root of 978691 is about 99.2845941496.

The spelling of 978691 in words is "nine hundred seventy-eight thousand, six hundred ninety-one".