211040021 has 4 divisors (see below), whose sum is σ = 211305612. Its totient is φ = 210774432.

The previous prime is 211039999. The next prime is 211040051. The reversal of 211040021 is 120040112.

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 149181796 + 61858225 = 12214^2 + 7865^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-211040021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 211039984 and 211040011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (211040051) 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 in 3 ways as a sum of consecutive naturals, for example, 131600 + ... + 133193.

It is an arithmetic number, because the mean of its divisors is an integer number (52826403).

Almost surely, 2^211040021 is an apocalyptic number.

It is an amenable number.

211040021 is a deficient number, since it is larger than the sum of its proper divisors (265591).

211040021 is an equidigital number, since it uses as much as digits as its factorization.

211040021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 265590.

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 211040021 is about 14527.2165606492. The cubic root of 211040021 is about 595.3718185383.

Adding to 211040021 its reverse (120040112), we get a palindrome (331080133).

Subtracting from 211040021 its reverse (120040112), we obtain a palindrome (90999909).

The spelling of 211040021 in words is "two hundred eleven million, forty thousand, twenty-one".