199921823 has 4 divisors (see below), whose sum is σ = 199977120. Its totient is φ = 199866528.

The previous prime is 199921807. The next prime is 199921831. The reversal of 199921823 is 328129991.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 328129991 = 7 ⋅46875713.

It is a cyclic number.

It is not a de Polignac number, because 199921823 - 2⁴ = 199921807 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 (199941823) 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, 21815 + ... + 29592.

It is an arithmetic number, because the mean of its divisors is an integer number (49994280).

Almost surely, 2^199921823 is an apocalyptic number.

199921823 is a deficient number, since it is larger than the sum of its proper divisors (55297).

199921823 is an equidigital number, since it uses as much as digits as its factorization.

199921823 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55296.

The product of its digits is 69984, while the sum is 44.

The square root of 199921823 is about 14139.3713792375. The cubic root of 199921823 is about 584.7273407341.

The spelling of 199921823 in words is "one hundred ninety-nine million, nine hundred twenty-one thousand, eight hundred twenty-three".