19978 has 8 divisors (see below), whose sum is σ = 34272. Its totient is φ = 8556.

The previous prime is 19973. The next prime is 19979. The reversal of 19978 is 87991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (19973) 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, 700 + ... + 727.

It is an arithmetic number, because the mean of its divisors is an integer number (4284).

2¹⁹⁹⁷⁸ is an apocalyptic number.

19978 is a deficient number, since it is larger than the sum of its proper divisors (14294).

19978 is a wasteful number, since it uses less digits than its factorization.

19978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1436.

The product of its digits is 4536, while the sum is 34.

The square root of 19978 is about 141.3435530896. The cubic root of 19978 is about 27.1342196497.

The spelling of 19978 in words is "nineteen thousand, nine hundred seventy-eight".