199451921 has 4 divisors (see below), whose sum is σ = 204316644. Its totient is φ = 194587200.

The previous prime is 199451887. The next prime is 199451947. The reversal of 199451921 is 129154991.

It is a happy number.

199451921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 129154991 = 7 ⋅18450713.

It can be written as a sum of positive squares in 2 ways, for example, as 102232321 + 97219600 = 10111^2 + 9860^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-199451921 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41), and also a Moran number because the ratio is a prime number: 4864681 = 199451921 / (1 + 9 + 9 + 4 + 5 + 1 + 9 + 2 + 1).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (199451951) 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, 2432300 + ... + 2432381.

It is an arithmetic number, because the mean of its divisors is an integer number (51079161).

Almost surely, 2^199451921 is an apocalyptic number.

It is an amenable number.

199451921 is a deficient number, since it is larger than the sum of its proper divisors (4864723).

199451921 is an equidigital number, since it uses as much as digits as its factorization.

199451921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4864722.

The product of its digits is 29160, while the sum is 41.

The square root of 199451921 is about 14122.7448111194. The cubic root of 199451921 is about 584.2688613549.

The spelling of 199451921 in words is "one hundred ninety-nine million, four hundred fifty-one thousand, nine hundred twenty-one".