21232809 has 24 divisors (see below), whose sum is σ = 33251400. Its totient is φ = 12978432.

The previous prime is 21232781. The next prime is 21232817. The reversal of 21232809 is 90823212.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 8294400 + 12938409 = 2880^2 + 3597^2 .

It is not a de Polignac number, because 21232809 - 2⁵ = 21232777 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21232829) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19717 + ... + 20765.

It is an arithmetic number, because the mean of its divisors is an integer number (1385475).

Almost surely, 2^21232809 is an apocalyptic number.

It is an amenable number.

21232809 is a deficient number, since it is larger than the sum of its proper divisors (12018591).

21232809 is a wasteful number, since it uses less digits than its factorization.

21232809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1241 (or 1238 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21232809 is about 4607.9072256286. The cubic root of 21232809 is about 276.9082007144.

The spelling of 21232809 in words is "twenty-one million, two hundred thirty-two thousand, eight hundred nine".