199901021 has 2 divisors, whose sum is σ = 199901022. Its totient is φ = 199901020.

The previous prime is 199901017. The next prime is 199901029. The reversal of 199901021 is 120109991.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 107952100 + 91948921 = 10390^2 + 9589^2 .

It is an emirp because it is prime and its reverse (120109991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 199901021 - 2² = 199901017 is a prime.

It is equal to p_11073695 and since 199901021 and 11073695 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199901029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99950510 + 99950511.

It is an arithmetic number, because the mean of its divisors is an integer number (99950511).

Almost surely, 2^199901021 is an apocalyptic number.

It is an amenable number.

199901021 is a deficient number, since it is larger than the sum of its proper divisors (1).

199901021 is an equidigital number, since it uses as much as digits as its factorization.

199901021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1458, while the sum is 32.

The square root of 199901021 is about 14138.6357545557. The cubic root of 199901021 is about 584.7070596064.

The spelling of 199901021 in words is "one hundred ninety-nine million, nine hundred one thousand, twenty-one".