21405011 has 4 divisors (see below), whose sum is σ = 21497112. Its totient is φ = 21312912.

The previous prime is 21404983. The next prime is 21405047. The reversal of 21405011 is 11050412.

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 21405011 - 2¹⁸ = 21142867 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21405511) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45701 + ... + 46166.

It is an arithmetic number, because the mean of its divisors is an integer number (5374278).

Almost surely, 2^21405011 is an apocalyptic number.

21405011 is a deficient number, since it is larger than the sum of its proper divisors (92101).

21405011 is an equidigital number, since it uses as much as digits as its factorization.

21405011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92100.

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21405011 is about 4626.5549818412. The cubic root of 21405011 is about 277.6547782492.

Adding to 21405011 its reverse (11050412), we get a palindrome (32455423).

The spelling of 21405011 in words is "twenty-one million, four hundred five thousand, eleven".