21323021 has 2 divisors, whose sum is σ = 21323022. Its totient is φ = 21323020.

The previous prime is 21323011. The next prime is 21323053. The reversal of 21323021 is 12032312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19669225 + 1653796 = 4435^2 + 1286^2 .

It is a cyclic number.

It is not a de Polignac number, because 21323021 - 2²² = 17128717 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21322987 and 21323005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21323011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10661510 + 10661511.

It is an arithmetic number, because the mean of its divisors is an integer number (10661511).

Almost surely, 2^21323021 is an apocalyptic number.

It is an amenable number.

21323021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21323021 is an equidigital number, since it uses as much as digits as its factorization.

21323021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 14.

The square root of 21323021 is about 4617.6856757471. The cubic root of 21323021 is about 277.2998139590.

Adding to 21323021 its reverse (12032312), we get a palindrome (33355333).

The spelling of 21323021 in words is "twenty-one million, three hundred twenty-three thousand, twenty-one".