21021011 has 16 divisors (see below), whose sum is σ = 25194240. Its totient is φ = 17313120.

The previous prime is 21021001. The next prime is 21021043. The reversal of 21021011 is 11012012.

It is not a de Polignac number, because 21021011 - 2⁶ = 21020947 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 21021011.

It is not an unprimeable number, because it can be changed into a prime (21021001) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2621 + ... + 6993.

It is an arithmetic number, because the mean of its divisors is an integer number (1574640).

Almost surely, 2^21021011 is an apocalyptic number.

21021011 is a deficient number, since it is larger than the sum of its proper divisors (4173229).

21021011 is a wasteful number, since it uses less digits than its factorization.

21021011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4426.

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

The square root of 21021011 is about 4584.8676098662. The cubic root of 21021011 is about 275.9843992792.

Adding to 21021011 its reverse (11012012), we get a palindrome (32033023).

It can be divided in two parts, 2102 and 1011, that added together give a palindrome (3113).

The spelling of 21021011 in words is "twenty-one million, twenty-one thousand, eleven".