21233609 has 2 divisors, whose sum is σ = 21233610. Its totient is φ = 21233608.

The previous prime is 21233603. The next prime is 21233617. The reversal of 21233609 is 90633212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20839225 + 394384 = 4565^2 + 628^2 .

It is a cyclic number.

It is not a de Polignac number, because 21233609 - 2⁴ = 21233593 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (21233603) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10616804 + 10616805.

It is an arithmetic number, because the mean of its divisors is an integer number (10616805).

Almost surely, 2^21233609 is an apocalyptic number.

It is an amenable number.

21233609 is a deficient number, since it is larger than the sum of its proper divisors (1).

21233609 is an equidigital number, since it uses as much as digits as its factorization.

21233609 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 26.

The square root of 21233609 is about 4607.9940321142. The cubic root of 21233609 is about 276.9116784106.

The spelling of 21233609 in words is "twenty-one million, two hundred thirty-three thousand, six hundred nine".