21521011 has 2 divisors, whose sum is σ = 21521012. Its totient is φ = 21521010.

The previous prime is 21521009. The next prime is 21521033. The reversal of 21521011 is 11012512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21521011 - 2¹ = 21521009 is a prime.

Together with 21521009, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21520982 and 21521000.

It is not a weakly prime, because it can be changed into another prime (21521041) 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 as a sum of consecutive naturals, namely, 10760505 + 10760506.

It is an arithmetic number, because the mean of its divisors is an integer number (10760506).

Almost surely, 2^21521011 is an apocalyptic number.

21521011 is a deficient number, since it is larger than the sum of its proper divisors (1).

21521011 is an equidigital number, since it uses as much as digits as its factorization.

21521011 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 20, while the sum is 13.

The square root of 21521011 is about 4639.0743688801. The cubic root of 21521011 is about 278.1554390117.

Adding to 21521011 its reverse (11012512), we get a palindrome (32533523).

The spelling of 21521011 in words is "twenty-one million, five hundred twenty-one thousand, eleven".