79978 has 4 divisors (see below), whose sum is σ = 119970. Its totient is φ = 39988.

The previous prime is 79973. The next prime is 79979. The reversal of 79978 is 87997.

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

It can be written as a sum of positive squares in only one way, i.e., 76729 + 3249 = 277^2 + 57^2 .

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 79978.

It is not an unprimeable number, because it can be changed into a prime (79973) by changing a digit.

79978 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 19993 + ... + 19996.

2⁷⁹⁹⁷⁸ is an apocalyptic number.

79978 is a deficient number, since it is larger than the sum of its proper divisors (39992).

79978 is a wasteful number, since it uses less digits than its factorization.

79978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39991.

The product of its digits is 31752, while the sum is 40.

The square root of 79978 is about 282.8038189275. The cubic root of 79978 is about 43.0847436416.

The spelling of 79978 in words is "seventy-nine thousand, nine hundred seventy-eight".