21051603 has 12 divisors (see below), whose sum is σ = 31222920. Its totient is φ = 14018508.

The previous prime is 21051599. The next prime is 21051623. The reversal of 21051603 is 30615012.

It is a powerful number, because all its prime factors have an exponent greater than 1 and also an Achilles number because it is not a perfect power.

21051603 is a `hidden beast` number, since 2 + 10 + 51 + 603 = 666.

It is not a de Polignac number, because 21051603 - 2² = 21051599 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21051623) 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 11 ways as a sum of consecutive naturals, for example, 23400 + ... + 24282.

It is an arithmetic number, because the mean of its divisors is an integer number (2601910).

Almost surely, 2^21051603 is an apocalyptic number.

21051603 is a deficient number, since it is larger than the sum of its proper divisors (10171317).

21051603 is an frugal number, since it uses more digits than its factorization.

21051603 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1775 (or 886 counting only the distinct ones).

The product of its (nonzero) digits is 180, while the sum is 18.

The square root of 21051603 is about 4588.2025892500. The cubic root of 21051603 is about 276.1182149550.

Adding to 21051603 its reverse (30615012), we get a palindrome (51666615).

The spelling of 21051603 in words is "twenty-one million, fifty-one thousand, six hundred three".