21102011 has 4 divisors (see below), whose sum is σ = 24116592. Its totient is φ = 18087432.

The previous prime is 21101963. The next prime is 21102023. The reversal of 21102011 is 11020112.

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

It is a cyclic number.

It is not a de Polignac number, because 21102011 - 2¹⁸ = 20839867 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21102011.

It is not an unprimeable number, because it can be changed into a prime (21102071) 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, 1507280 + ... + 1507293.

It is an arithmetic number, because the mean of its divisors is an integer number (6029148).

Almost surely, 2^21102011 is an apocalyptic number.

21102011 is a deficient number, since it is larger than the sum of its proper divisors (3014581).

21102011 is an equidigital number, since it uses as much as digits as its factorization.

21102011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3014580.

The product of its (nonzero) digits is 4, while the sum is 8.

The square root of 21102011 is about 4593.6925234500. The cubic root of 21102011 is about 276.3384273605.

Adding to 21102011 its reverse (11020112), we get a palindrome (32122123).

It can be divided in two parts, 2 and 1102011, that multiplied together give a palindrome (2204022).

The spelling of 21102011 in words is "twenty-one million, one hundred two thousand, eleven".