199240721 has 4 divisors (see below), whose sum is σ = 199356132. Its totient is φ = 199125312.

The previous prime is 199240711. The next prime is 199240729. The reversal of 199240721 is 127042991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 127042991 = 31 ⋅4098161.

It can be written as a sum of positive squares in 2 ways, for example, as 78570496 + 120670225 = 8864^2 + 10985^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-199240721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (199240729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 55076 + ... + 58581.

It is an arithmetic number, because the mean of its divisors is an integer number (49839033).

Almost surely, 2^199240721 is an apocalyptic number.

It is an amenable number.

199240721 is a deficient number, since it is larger than the sum of its proper divisors (115411).

199240721 is a wasteful number, since it uses less digits than its factorization.

199240721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115410.

The product of its (nonzero) digits is 9072, while the sum is 35.

The square root of 199240721 is about 14115.2655306232. The cubic root of 199240721 is about 584.0625607356.

The spelling of 199240721 in words is "one hundred ninety-nine million, two hundred forty thousand, seven hundred twenty-one".