21917389 has 4 divisors (see below), whose sum is σ = 23603356. Its totient is φ = 20231424.

The previous prime is 21917351. The next prime is 21917419. The reversal of 21917389 is 98371912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12369289 + 9548100 = 3517^2 + 3090^2 .

It is a cyclic number.

It is not a de Polignac number, because 21917389 - 2⁹ = 21916877 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 (21917339) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 842964 + ... + 842989.

It is an arithmetic number, because the mean of its divisors is an integer number (5900839).

Almost surely, 2^21917389 is an apocalyptic number.

It is an amenable number.

21917389 is a deficient number, since it is larger than the sum of its proper divisors (1685967).

21917389 is a wasteful number, since it uses less digits than its factorization.

21917389 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1685966.

The product of its digits is 27216, while the sum is 40.

The square root of 21917389 is about 4681.6011150033. The cubic root of 21917389 is about 279.8527669815.

The spelling of 21917389 in words is "twenty-one million, nine hundred seventeen thousand, three hundred eighty-nine".