199997521 has 2 divisors, whose sum is σ = 199997522. Its totient is φ = 199997520.

The previous prime is 199997513. The next prime is 199997531. The reversal of 199997521 is 125799991.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 174636225 + 25361296 = 13215^2 + 5036^2 .

It is an emirp because it is prime and its reverse (125799991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 199997521 - 2³ = 199997513 is a prime.

It is a super-2 number, since 2×199997521² = 79998016812290882, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (199997531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99998760 + 99998761.

It is an arithmetic number, because the mean of its divisors is an integer number (99998761).

Almost surely, 2^199997521 is an apocalyptic number.

It is an amenable number.

199997521 is a deficient number, since it is larger than the sum of its proper divisors (1).

199997521 is an equidigital number, since it uses as much as digits as its factorization.

199997521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 459270, while the sum is 52.

The square root of 199997521 is about 14142.0479775738. The cubic root of 199997521 is about 584.8011314193.

The spelling of 199997521 in words is "one hundred ninety-nine million, nine hundred ninety-seven thousand, five hundred twenty-one".