21204023 has 4 divisors (see below), whose sum is σ = 21304728. Its totient is φ = 21103320.

The previous prime is 21204013. The next prime is 21204037. The reversal of 21204023 is 32040212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21204023 is a prime.

It is a super-2 number, since 2×21204023² = 899221182769058, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21203989 and 21204007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21204013) 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, 50036 + ... + 50457.

It is an arithmetic number, because the mean of its divisors is an integer number (5326182).

Almost surely, 2^21204023 is an apocalyptic number.

21204023 is a deficient number, since it is larger than the sum of its proper divisors (100705).

21204023 is a wasteful number, since it uses less digits than its factorization.

21204023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 100704.

The product of its (nonzero) digits is 96, while the sum is 14.

The square root of 21204023 is about 4604.7826224481. The cubic root of 21204023 is about 276.7830063450.

Adding to 21204023 its reverse (32040212), we get a palindrome (53244235).

The spelling of 21204023 in words is "twenty-one million, two hundred four thousand, twenty-three".