978661 has 4 divisors (see below), whose sum is σ = 984492. Its totient is φ = 972832.

The previous prime is 978647. The next prime is 978683. The reversal of 978661 is 166879.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 166879 = 109 ⋅1531.

It can be written as a sum of positive squares in 2 ways, for example, as 497025 + 481636 = 705^2 + 694^2 .

It is a cyclic number.

It is not a de Polignac number, because 978661 - 2⁹ = 978149 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a nialpdrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 978661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (978611) 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, 2656 + ... + 3001.

It is an arithmetic number, because the mean of its divisors is an integer number (246123).

2⁹⁷⁸⁶⁶¹ is an apocalyptic number.

It is an amenable number.

978661 is a deficient number, since it is larger than the sum of its proper divisors (5831).

978661 is a wasteful number, since it uses less digits than its factorization.

978661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5830.

The product of its digits is 18144, while the sum is 37.

The square root of 978661 is about 989.2729653640. The cubic root of 978661 is about 99.2835796761.

The spelling of 978661 in words is "nine hundred seventy-eight thousand, six hundred sixty-one".