19981978138 has 8 divisors (see below), whose sum is σ = 30670013088. Its totient is φ = 9758640444.

The previous prime is 19981978099. The next prime is 19981978139. The reversal of 19981978138 is 83187918991.

It is a happy number.

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

It is a self number, because there is not a number n which added to its sum of digits gives 19981978138.

It is not an unprimeable number, because it can be changed into a prime (19981978139) 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, 116174206 + ... + 116174377.

It is an arithmetic number, because the mean of its divisors is an integer number (3833751636).

Almost surely, 2^19981978138 is an apocalyptic number.

19981978138 is a deficient number, since it is larger than the sum of its proper divisors (10688034950).

19981978138 is a wasteful number, since it uses less digits than its factorization.

19981978138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 232348628.

The product of its digits is 7838208, while the sum is 64.

The spelling of 19981978138 in words is "nineteen billion, nine hundred eighty-one million, nine hundred seventy-eight thousand, one hundred thirty-eight".