21000011 has 8 divisors (see below), whose sum is σ = 21395520. Its totient is φ = 20607048.

The previous prime is 20999999. The next prime is 21000037. The reversal of 21000011 is 11000012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21000011 - 2¹⁸ = 20737867 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20999959 and 21000004.

It is not an unprimeable number, because it can be changed into a prime (21000041) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 24980 + ... + 25806.

It is an arithmetic number, because the mean of its divisors is an integer number (2674440).

Almost surely, 2^21000011 is an apocalyptic number.

21000011 is a deficient number, since it is larger than the sum of its proper divisors (395509).

21000011 is an equidigital number, since it uses as much as digits as its factorization.

21000011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1273.

The product of its (nonzero) digits is 2, while the sum is 5.

The square root of 21000011 is about 4582.5768951541. The cubic root of 21000011 is about 275.8924658098.

Adding to 21000011 its reverse (11000012), we get a palindrome (32000023).

Subtracting from 21000011 its reverse (11000012), we obtain a palindrome (9999999).

Multiplying 21000011 by its reverse (11000012), we get a palindrome (231000373000132).

The spelling of 21000011 in words is "twenty-one million, eleven", and thus it is an aban number and an uban number.