21089905 has 8 divisors (see below), whose sum is σ = 26640000. Its totient is φ = 15983856.

The previous prime is 21089903. The next prime is 21089921. The reversal of 21089905 is 50998012.

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 21089905 - 2¹ = 21089903 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21089903) 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, 110905 + ... + 111094.

It is an arithmetic number, because the mean of its divisors is an integer number (3330000).

Almost surely, 2^21089905 is an apocalyptic number.

It is an amenable number.

21089905 is a deficient number, since it is larger than the sum of its proper divisors (5550095).

21089905 is a wasteful number, since it uses less digits than its factorization.

21089905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 222023.

The product of its (nonzero) digits is 6480, while the sum is 34.

The square root of 21089905 is about 4592.3746580609. The cubic root of 21089905 is about 276.2855731099.

The spelling of 21089905 in words is "twenty-one million, eighty-nine thousand, nine hundred five".