199691521 has 2 divisors, whose sum is σ = 199691522. Its totient is φ = 199691520.

The previous prime is 199691519. The next prime is 199691533. The reversal of 199691521 is 125196991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 127441521 + 72250000 = 11289^2 + 8500^2 .

It is a cyclic number.

It is not a de Polignac number, because 199691521 - 2¹ = 199691519 is a prime.

Together with 199691519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (199691581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99845760 + 99845761.

It is an arithmetic number, because the mean of its divisors is an integer number (99845761).

Almost surely, 2^199691521 is an apocalyptic number.

It is an amenable number.

199691521 is a deficient number, since it is larger than the sum of its proper divisors (1).

199691521 is an equidigital number, since it uses as much as digits as its factorization.

199691521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 43740, while the sum is 43.

The square root of 199691521 is about 14131.2250353605. The cubic root of 199691521 is about 584.5027269054.

The spelling of 199691521 in words is "one hundred ninety-nine million, six hundred ninety-one thousand, five hundred twenty-one".