19999823 has 4 divisors (see below), whose sum is σ = 20134200. Its totient is φ = 19865448.

The previous prime is 19999817. The next prime is 19999831. The reversal of 19999823 is 32899991.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19999823 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19999843) 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, 66965 + ... + 67262.

It is an arithmetic number, because the mean of its divisors is an integer number (5033550).

Almost surely, 2^19999823 is an apocalyptic number.

19999823 is a deficient number, since it is larger than the sum of its proper divisors (134377).

19999823 is a wasteful number, since it uses less digits than its factorization.

19999823 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134376.

The product of its digits is 314928, while the sum is 50.

The square root of 19999823 is about 4472.1161657542. The cubic root of 19999823 is about 271.4409609039.

It can be divided in two parts, 199998 and 23, that multiplied together give a palindrome (4599954).

The spelling of 19999823 in words is "nineteen million, nine hundred ninety-nine thousand, eight hundred twenty-three".