21909245 has 8 divisors (see below), whose sum is σ = 26316384. Its totient is φ = 17510544.

The previous prime is 21909229. The next prime is 21909247. The reversal of 21909245 is 54290912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21909245 - 2⁴ = 21909229 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21909247) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8162 + ... + 10508.

It is an arithmetic number, because the mean of its divisors is an integer number (3289548).

Almost surely, 2^21909245 is an apocalyptic number.

It is an amenable number.

21909245 is a deficient number, since it is larger than the sum of its proper divisors (4407139).

21909245 is a wasteful number, since it uses less digits than its factorization.

21909245 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4219.

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 21909245 is about 4680.7312462905. The cubic root of 21909245 is about 279.8181003935.

The spelling of 21909245 in words is "twenty-one million, nine hundred nine thousand, two hundred forty-five".