978117691 has 4 divisors (see below), whose sum is σ = 978877800. Its totient is φ = 977357584.

The previous prime is 978117683. The next prime is 978117727. The reversal of 978117691 is 196711879.

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 978117691 - 2³ = 978117683 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (978117671) 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, 378121 + ... + 380698.

It is an arithmetic number, because the mean of its divisors is an integer number (244719450).

Almost surely, 2^978117691 is an apocalyptic number.

978117691 is a deficient number, since it is larger than the sum of its proper divisors (760109).

978117691 is a wasteful number, since it uses less digits than its factorization.

978117691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 760108.

The product of its digits is 190512, while the sum is 49.

The square root of 978117691 is about 31274.8731572168. The cubic root of 978117691 is about 992.6520366802.

It can be divided in two parts, 9781 and 17691, that added together give a palindrome (27472).

The spelling of 978117691 in words is "nine hundred seventy-eight million, one hundred seventeen thousand, six hundred ninety-one".