19991939 has 4 divisors (see below), whose sum is σ = 21809400. Its totient is φ = 18174480.

The previous prime is 19991911. The next prime is 19991963. The reversal of 19991939 is 93919991.

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

It is a cyclic number.

It is not a de Polignac number, because 19991939 - 2²⁰ = 18943363 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19991989) 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, 908714 + ... + 908735.

It is an arithmetic number, because the mean of its divisors is an integer number (5452350).

Almost surely, 2^19991939 is an apocalyptic number.

19991939 is a deficient number, since it is larger than the sum of its proper divisors (1817461).

19991939 is a wasteful number, since it uses less digits than its factorization.

19991939 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1817460.

The product of its digits is 177147, while the sum is 50.

The square root of 19991939 is about 4471.2346169710. The cubic root of 19991939 is about 271.4052885582.

The spelling of 19991939 in words is "nineteen million, nine hundred ninety-one thousand, nine hundred thirty-nine".