978940691 has 4 divisors (see below), whose sum is σ = 979597872. Its totient is φ = 978283512.

The previous prime is 978940681. The next prime is 978940693. The reversal of 978940691 is 196049879.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 196049879 = 149 ⋅1315771.

It is a cyclic number.

It is not a de Polignac number, because 978940691 - 2¹⁰ = 978939667 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (978940693) 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, 326351 + ... + 329336.

It is an arithmetic number, because the mean of its divisors is an integer number (244899468).

Almost surely, 2^978940691 is an apocalyptic number.

978940691 is a deficient number, since it is larger than the sum of its proper divisors (657181).

978940691 is a wasteful number, since it uses less digits than its factorization.

978940691 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 657180.

The product of its (nonzero) digits is 979776, while the sum is 53.

The square root of 978940691 is about 31288.0279180392. The cubic root of 978940691 is about 992.9303684220.

The spelling of 978940691 in words is "nine hundred seventy-eight million, nine hundred forty thousand, six hundred ninety-one".