21003423 has 32 divisors (see below), whose sum is σ = 33094656. Its totient is φ = 11601408.

The previous prime is 21003413. The next prime is 21003427. The reversal of 21003423 is 32430012.

It is not a de Polignac number, because 21003423 - 2⁹ = 21002911 is a prime.

It is a super-2 number, since 2×21003423² = 882287555433858, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21003427) 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 31 ways as a sum of consecutive naturals, for example, 125686 + ... + 125852.

It is an arithmetic number, because the mean of its divisors is an integer number (1034208).

Almost surely, 2^21003423 is an apocalyptic number.

21003423 is a deficient number, since it is larger than the sum of its proper divisors (12091233).

21003423 is a wasteful number, since it uses less digits than its factorization.

21003423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 343.

The product of its (nonzero) digits is 144, while the sum is 15.

The square root of 21003423 is about 4582.9491596569. The cubic root of 21003423 is about 275.9074069784.

Adding to 21003423 its reverse (32430012), we get a palindrome (53433435).

The spelling of 21003423 in words is "twenty-one million, three thousand, four hundred twenty-three".