21051803 has 4 divisors (see below), whose sum is σ = 21099768. Its totient is φ = 21003840.

The previous prime is 21051799. The next prime is 21051809. The reversal of 21051803 is 30815012.

21051803 is nontrivially palindromic in base 7.

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 21051803 - 2² = 21051799 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21051809) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23318 + ... + 24203.

It is an arithmetic number, because the mean of its divisors is an integer number (5274942).

Almost surely, 2^21051803 is an apocalyptic number.

21051803 is a deficient number, since it is larger than the sum of its proper divisors (47965).

21051803 is an equidigital number, since it uses as much as digits as its factorization.

21051803 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47964.

The product of its (nonzero) digits is 240, while the sum is 20.

The square root of 21051803 is about 4588.2243842253. The cubic root of 21051803 is about 276.1190893693.

Adding to 21051803 its reverse (30815012), we get a palindrome (51866815).

The spelling of 21051803 in words is "twenty-one million, fifty-one thousand, eight hundred three".