21001011 has 4 divisors (see below), whose sum is σ = 28001352. Its totient is φ = 14000672.

The previous prime is 21000983. The next prime is 21001021. The reversal of 21001011 is 11010012.

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 21001011 - 2⁷ = 21000883 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21001021) 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, 3500166 + ... + 3500171.

It is an arithmetic number, because the mean of its divisors is an integer number (7000338).

Almost surely, 2^21001011 is an apocalyptic number.

21001011 is a deficient number, since it is larger than the sum of its proper divisors (7000341).

21001011 is an equidigital number, since it uses as much as digits as its factorization.

21001011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7000340.

The product of its (nonzero) digits is 2, while the sum is 6.

The square root of 21001011 is about 4582.6860027717. The cubic root of 21001011 is about 275.8968449835.

Adding to 21001011 its reverse (11010012), we get a palindrome (32011023).

Subtracting from 21001011 its reverse (11010012), we obtain a palindrome (9990999).

Multiplying 21001011 by its reverse (11010012), we get a palindrome (231221383122132).

The spelling of 21001011 in words is "twenty-one million, one thousand, eleven".