21309433 has 2 divisors, whose sum is σ = 21309434. Its totient is φ = 21309432.

The previous prime is 21309401. The next prime is 21309437. The reversal of 21309433 is 33490312.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16949689 + 4359744 = 4117^2 + 2088^2 .

It is a cyclic number.

It is not a de Polignac number, because 21309433 - 2⁵ = 21309401 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21309398 and 21309407.

It is not a weakly prime, because it can be changed into another prime (21309437) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10654716 + 10654717.

It is an arithmetic number, because the mean of its divisors is an integer number (10654717).

Almost surely, 2^21309433 is an apocalyptic number.

It is an amenable number.

21309433 is a deficient number, since it is larger than the sum of its proper divisors (1).

21309433 is an equidigital number, since it uses as much as digits as its factorization.

21309433 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 25.

The square root of 21309433 is about 4616.2141414800. The cubic root of 21309433 is about 277.2408987530.

Adding to 21309433 its reverse (33490312), we get a palindrome (54799745).

The spelling of 21309433 in words is "twenty-one million, three hundred nine thousand, four hundred thirty-three".