19978118 has 4 divisors (see below), whose sum is σ = 29967180. Its totient is φ = 9989058.

The previous prime is 19978117. The next prime is 19978121. The reversal of 19978118 is 81187991.

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

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19978117) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4994528 + ... + 4994531.

It is an arithmetic number, because the mean of its divisors is an integer number (7491795).

Almost surely, 2^19978118 is an apocalyptic number.

19978118 is a deficient number, since it is larger than the sum of its proper divisors (9989062).

19978118 is an equidigital number, since it uses as much as digits as its factorization.

19978118 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9989061.

The product of its digits is 36288, while the sum is 44.

The square root of 19978118 is about 4469.6888034851. The cubic root of 19978118 is about 271.3427307236.

The spelling of 19978118 in words is "nineteen million, nine hundred seventy-eight thousand, one hundred eighteen".