21021611 has 4 divisors (see below), whose sum is σ = 22638672. Its totient is φ = 19404552.

The previous prime is 21021601. The next prime is 21021617. The reversal of 21021611 is 11612012.

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 21021611 - 2¹⁴ = 21005227 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21021617) 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, 808511 + ... + 808536.

It is an arithmetic number, because the mean of its divisors is an integer number (5659668).

Almost surely, 2^21021611 is an apocalyptic number.

21021611 is a deficient number, since it is larger than the sum of its proper divisors (1617061).

21021611 is a wasteful number, since it uses less digits than its factorization.

21021611 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1617060.

The product of its (nonzero) digits is 24, while the sum is 14.

The square root of 21021611 is about 4584.9330420411. The cubic root of 21021611 is about 275.9870250499.

Adding to 21021611 its reverse (11612012), we get a palindrome (32633623).

The spelling of 21021611 in words is "twenty-one million, twenty-one thousand, six hundred eleven".