21005105 has 8 divisors (see below), whose sum is σ = 27497664. Its totient is φ = 15276400.

The previous prime is 21005087. The next prime is 21005111. The reversal of 21005105 is 50150012.

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

It is not a de Polignac number, because 21005105 - 2⁶ = 21005041 is a prime.

It is a super-2 number, since 2×21005105² = 882428872122050, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21005105.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 190901 + ... + 191010.

It is an arithmetic number, because the mean of its divisors is an integer number (3437208).

Almost surely, 2^21005105 is an apocalyptic number.

It is an amenable number.

21005105 is a deficient number, since it is larger than the sum of its proper divisors (6492559).

21005105 is a wasteful number, since it uses less digits than its factorization.

21005105 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 381927.

The product of its (nonzero) digits is 50, while the sum is 14.

The square root of 21005105 is about 4583.1326622737. The cubic root of 21005105 is about 275.9147718711.

Adding to 21005105 its reverse (50150012), we get a palindrome (71155117).

The spelling of 21005105 in words is "twenty-one million, five thousand, one hundred five".