19881918 has 24 divisors (see below), whose sum is σ = 49231728. Its totient is φ = 5680512.

The previous prime is 19881889. The next prime is 19881929. The reversal of 19881918 is 81918891.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 78771 + ... + 79022.

It is an arithmetic number, because the mean of its divisors is an integer number (2051322).

Almost surely, 2^19881918 is an apocalyptic number.

19881918 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

19881918 is an abundant number, since it is smaller than the sum of its proper divisors (29349810).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

19881918 is a wasteful number, since it uses less digits than its factorization.

19881918 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 157808 (or 157805 counting only the distinct ones).

The product of its digits is 41472, while the sum is 45.

The square root of 19881918 is about 4458.9144418793. The cubic root of 19881918 is about 270.9065004263.

The spelling of 19881918 in words is "nineteen million, eight hundred eighty-one thousand, nine hundred eighteen".