2001111821 has 2 divisors, whose sum is σ = 2001111822. Its totient is φ = 2001111820.

The previous prime is 2001111799. The next prime is 2001111829. The reversal of 2001111821 is 1281111002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1965946921 + 35164900 = 44339^2 + 5930^2 .

It is a cyclic number.

It is not a de Polignac number, because 2001111821 - 2³⁰ = 927369997 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 2001111821.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2001111829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1000555910 + 1000555911.

It is an arithmetic number, because the mean of its divisors is an integer number (1000555911).

Almost surely, 2^2001111821 is an apocalyptic number.

It is an amenable number.

2001111821 is a deficient number, since it is larger than the sum of its proper divisors (1).

2001111821 is an equidigital number, since it uses as much as digits as its factorization.

2001111821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 32, while the sum is 17.

The square root of 2001111821 is about 44733.7883595834. The cubic root of 2001111821 is about 1260.1544744261.

Adding to 2001111821 its reverse (1281111002), we get a palindrome (3282222823).

The spelling of 2001111821 in words is "two billion, one million, one hundred eleven thousand, eight hundred twenty-one".