21011005 has 16 divisors (see below), whose sum is σ = 26115120. Its totient is φ = 16215552.

The previous prime is 21010987. The next prime is 21011009. The reversal of 21011005 is 50011012.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 1172889 + 19838116 = 1083^2 + 4454^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011005 - 2⁵ = 21010973 is a prime.

It is a super-2 number, since 2×21011005² = 882924662220050, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21010982 and 21011000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21011009) 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 15 ways as a sum of consecutive naturals, for example, 24931 + ... + 25759.

It is an arithmetic number, because the mean of its divisors is an integer number (1632195).

Almost surely, 2^21011005 is an apocalyptic number.

It is an amenable number.

21011005 is a deficient number, since it is larger than the sum of its proper divisors (5104115).

21011005 is a wasteful number, since it uses less digits than its factorization.

21011005 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1008.

The product of its (nonzero) digits is 10, while the sum is 10.

The square root of 21011005 is about 4583.7762816263. The cubic root of 21011005 is about 275.9406028102.

Adding to 21011005 its reverse (50011012), we get a palindrome (71022017).

The spelling of 21011005 in words is "twenty-one million, eleven thousand, five".