21012011 has 4 divisors (see below), whose sum is σ = 21198072. Its totient is φ = 20825952.

The previous prime is 21011981. The next prime is 21012053. The reversal of 21012011 is 11021012.

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 21012011 - 2¹⁰ = 21010987 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 21012011.

It is not an unprimeable number, because it can be changed into a prime (21012091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 92861 + ... + 93086.

It is an arithmetic number, because the mean of its divisors is an integer number (5299518).

Almost surely, 2^21012011 is an apocalyptic number.

21012011 is a deficient number, since it is larger than the sum of its proper divisors (186061).

21012011 is a wasteful number, since it uses less digits than its factorization.

21012011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 186060.

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

The square root of 21012011 is about 4583.8860151622. The cubic root of 21012011 is about 275.9450067216.

Adding to 21012011 its reverse (11021012), we get a palindrome (32033023).

Subtracting from 21012011 its reverse (11021012), we obtain a palindrome (9990999).

It can be divided in two parts, 210 and 12011, that added together give a palindrome (12221).

The spelling of 21012011 in words is "twenty-one million, twelve thousand, eleven".