21909447 has 40 divisors (see below), whose sum is σ = 39622176. Its totient is φ = 11778048.

The previous prime is 21909401. The next prime is 21909449. The reversal of 21909447 is 74490912.

It is not a de Polignac number, because 21909447 - 2¹⁰ = 21908423 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21909449) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 8503 + ... + 10775.

Almost surely, 2^21909447 is an apocalyptic number.

21909447 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21909447 is a deficient number, since it is larger than the sum of its proper divisors (17712729).

21909447 is a wasteful number, since it uses less digits than its factorization.

21909447 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2309 (or 2300 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21909447 is about 4680.7528240658. The cubic root of 21909447 is about 279.8189603513.

The spelling of 21909447 in words is "twenty-one million, nine hundred nine thousand, four hundred forty-seven".