21609337 has 4 divisors (see below), whose sum is σ = 22136436. Its totient is φ = 21082240.

The previous prime is 21609293. The next prime is 21609373. The reversal of 21609337 is 73390612.

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

It can be written as a sum of positive squares in 2 ways, for example, as 4145296 + 17464041 = 2036^2 + 4179^2 .

It is a cyclic number.

It is not a de Polignac number, because 21609337 - 2⁷ = 21609209 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21609299 and 21609308.

It is not an unprimeable number, because it can be changed into a prime (21609377) 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, 263488 + ... + 263569.

It is an arithmetic number, because the mean of its divisors is an integer number (5534109).

Almost surely, 2^21609337 is an apocalyptic number.

It is an amenable number.

21609337 is a deficient number, since it is larger than the sum of its proper divisors (527099).

21609337 is an equidigital number, since it uses as much as digits as its factorization.

21609337 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 527098.

The product of its (nonzero) digits is 6804, while the sum is 31.

The square root of 21609337 is about 4648.5844081828. The cubic root of 21609337 is about 278.5354524907.

Adding to 21609337 its reverse (73390612), we get a palindrome (94999949).

The spelling of 21609337 in words is "twenty-one million, six hundred nine thousand, three hundred thirty-seven".