19881985 has 4 divisors (see below), whose sum is σ = 23858388. Its totient is φ = 15905584.

The previous prime is 19881973. The next prime is 19882003. The reversal of 19881985 is 58918891.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 58918891 = 5869 ⋅10039.

It can be written as a sum of positive squares in 2 ways, for example, as 15752961 + 4129024 = 3969^2 + 2032^2 .

It is a cyclic number.

It is not a de Polignac number, because 19881985 - 2⁹ = 19881473 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1988194 + ... + 1988203.

It is an arithmetic number, because the mean of its divisors is an integer number (5964597).

It is a Proth number, since it is equal to 2427 ⋅ 2¹³ + 1 and 2427 < 2¹³.

Almost surely, 2^19881985 is an apocalyptic number.

It is an amenable number.

19881985 is a deficient number, since it is larger than the sum of its proper divisors (3976403).

19881985 is an equidigital number, since it uses as much as digits as its factorization.

19881985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3976402.

The product of its digits is 207360, while the sum is 49.

The square root of 19881985 is about 4458.9219549124. The cubic root of 19881985 is about 270.9068047349.

The spelling of 19881985 in words is "nineteen million, eight hundred eighty-one thousand, nine hundred eighty-five".