210001921 has 4 divisors (see below), whose sum is σ = 210053844. Its totient is φ = 209950000.

The previous prime is 210001879. The next prime is 210001933. The reversal of 210001921 is 129100012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 151019521 + 58982400 = 12289^2 + 7680^2 .

It is a cyclic number.

It is not a de Polignac number, because 210001921 - 2⁷ = 210001793 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 210001895 and 210001904.

It is not an unprimeable number, because it can be changed into a prime (210001951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19330 + ... + 28171.

It is an arithmetic number, because the mean of its divisors is an integer number (52513461).

Almost surely, 2^210001921 is an apocalyptic number.

It is an amenable number.

210001921 is a deficient number, since it is larger than the sum of its proper divisors (51923).

210001921 is an equidigital number, since it uses as much as digits as its factorization.

210001921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51922.

The product of its (nonzero) digits is 36, while the sum is 16.

The square root of 210001921 is about 14491.4430268348. The cubic root of 210001921 is about 594.3940076952.

Adding to 210001921 its reverse (129100012), we get a palindrome (339101933).

The spelling of 210001921 in words is "two hundred ten million, one thousand, nine hundred twenty-one".