21289917 has 8 divisors (see below), whose sum is σ = 30967200. Its totient is φ = 12902960.

The previous prime is 21289913. The next prime is 21289949. The reversal of 21289917 is 71998212.

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 21289917 - 2² = 21289913 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21289913) 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, 322542 + ... + 322607.

It is an arithmetic number, because the mean of its divisors is an integer number (3870900).

Almost surely, 2^21289917 is an apocalyptic number.

It is an amenable number.

21289917 is a deficient number, since it is larger than the sum of its proper divisors (9677283).

21289917 is a wasteful number, since it uses less digits than its factorization.

21289917 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 645163.

The product of its digits is 18144, while the sum is 39.

The square root of 21289917 is about 4614.0998038621. The cubic root of 21289917 is about 277.1562369356.

The spelling of 21289917 in words is "twenty-one million, two hundred eighty-nine thousand, nine hundred seventeen".