21732309 has 12 divisors (see below), whose sum is σ = 32756256. Its totient is φ = 13858152.

The previous prime is 21732253. The next prime is 21732317. The reversal of 21732309 is 90323712.

It is a de Polignac number, because none of the positive numbers 2^k-21732309 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21732349) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 52287 + ... + 52700.

It is an arithmetic number, because the mean of its divisors is an integer number (2729688).

Almost surely, 2^21732309 is an apocalyptic number.

It is an amenable number.

21732309 is a deficient number, since it is larger than the sum of its proper divisors (11023947).

21732309 is a wasteful number, since it uses less digits than its factorization.

21732309 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 105016 (or 105013 counting only the distinct ones).

The product of its (nonzero) digits is 2268, while the sum is 27.

The square root of 21732309 is about 4661.7924664232. The cubic root of 21732309 is about 279.0628062251.

The spelling of 21732309 in words is "twenty-one million, seven hundred thirty-two thousand, three hundred nine".