20101811 has 4 divisors (see below), whose sum is σ = 20110992. Its totient is φ = 20092632.

The previous prime is 20101771. The next prime is 20101817. The reversal of 20101811 is 11810102.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 11810102 = 2 ⋅5905051.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20101811 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20101817) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 821 + ... + 6393.

It is an arithmetic number, because the mean of its divisors is an integer number (5027748).

Almost surely, 2^20101811 is an apocalyptic number.

20101811 is a deficient number, since it is larger than the sum of its proper divisors (9181).

20101811 is an equidigital number, since it uses as much as digits as its factorization.

20101811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9180.

The product of its (nonzero) digits is 16, while the sum is 14.

The square root of 20101811 is about 4483.5043213986. The cubic root of 20101811 is about 271.9015782534.

Adding to 20101811 its reverse (11810102), we get a palindrome (31911913).

The spelling of 20101811 in words is "twenty million, one hundred one thousand, eight hundred eleven".