198403721 has 2 divisors, whose sum is σ = 198403722. Its totient is φ = 198403720.

The previous prime is 198403697. The next prime is 198403747. The reversal of 198403721 is 127304891.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 189337600 + 9066121 = 13760^2 + 3011^2 .

It is a cyclic number.

It is not a de Polignac number, because 198403721 - 2²⁶ = 131294857 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is equal to p_10995371 and since 198403721 and 10995371 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (198403921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99201860 + 99201861.

It is an arithmetic number, because the mean of its divisors is an integer number (99201861).

Almost surely, 2^198403721 is an apocalyptic number.

It is an amenable number.

198403721 is a deficient number, since it is larger than the sum of its proper divisors (1).

198403721 is an equidigital number, since it uses as much as digits as its factorization.

198403721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 12096, while the sum is 35.

The square root of 198403721 is about 14085.5855753320. The cubic root of 198403721 is about 583.2435405371.

The spelling of 198403721 in words is "one hundred ninety-eight million, four hundred three thousand, seven hundred twenty-one".