19997905 has 4 divisors (see below), whose sum is σ = 23997492. Its totient is φ = 15998320.

The previous prime is 19997897. The next prime is 19997911. The reversal of 19997905 is 50979991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 50979991 = 17 ⋅2998823.

It can be written as a sum of positive squares in 2 ways, for example, as 9186961 + 10810944 = 3031^2 + 3288^2 .

It is not a de Polignac number, because 19997905 - 2³ = 19997897 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, 1999786 + ... + 1999795.

It is an arithmetic number, because the mean of its divisors is an integer number (5999373).

Almost surely, 2^19997905 is an apocalyptic number.

It is an amenable number.

19997905 is a deficient number, since it is larger than the sum of its proper divisors (3999587).

19997905 is an equidigital number, since it uses as much as digits as its factorization.

19997905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3999586.

The product of its (nonzero) digits is 229635, while the sum is 49.

The square root of 19997905 is about 4471.9017207448. The cubic root of 19997905 is about 271.4322834870.

It can be divided in two parts, 19997 and 905, that added together give a palindrome (20902).

The spelling of 19997905 in words is "nineteen million, nine hundred ninety-seven thousand, nine hundred five".