21203105 has 16 divisors (see below), whose sum is σ = 31722624. Its totient is φ = 13217280.

The previous prime is 21203099. The next prime is 21203113. The reversal of 21203105 is 50130212.

It is a happy number.

It is not a de Polignac number, because 21203105 - 2⁶ = 21203041 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21203105.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27152 + ... + 27921.

It is an arithmetic number, because the mean of its divisors is an integer number (1982664).

Almost surely, 2^21203105 is an apocalyptic number.

It is an amenable number.

21203105 is a deficient number, since it is larger than the sum of its proper divisors (10519519).

21203105 is a wasteful number, since it uses less digits than its factorization.

21203105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55096.

The product of its (nonzero) digits is 60, while the sum is 14.

The square root of 21203105 is about 4604.6829423968. The cubic root of 21203105 is about 276.7790119699.

Adding to 21203105 its reverse (50130212), we get a palindrome (71333317).

It can be divided in two parts, 2120 and 3105, that added together give a palindrome (5225).

The spelling of 21203105 in words is "twenty-one million, two hundred three thousand, one hundred five".