21909081 has 8 divisors (see below), whose sum is σ = 29344000. Its totient is φ = 14540112.

The previous prime is 21909079. The next prime is 21909089. The reversal of 21909081 is 18090912.

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

It is not a de Polignac number, because 21909081 - 2¹ = 21909079 is a prime.

It is a super-2 number, since 2×21909081² = 960015660529122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21909089) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15706 + ... + 17043.

It is an arithmetic number, because the mean of its divisors is an integer number (3668000).

Almost surely, 2^21909081 is an apocalyptic number.

It is an amenable number.

21909081 is a deficient number, since it is larger than the sum of its proper divisors (7434919).

21909081 is a wasteful number, since it uses less digits than its factorization.

21909081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32975.

The product of its (nonzero) digits is 1296, while the sum is 30.

The square root of 21909081 is about 4680.7137276274. The cubic root of 21909081 is about 279.8174022060.

Adding to 21909081 its reverse (18090912), we get a palindrome (39999993).

The spelling of 21909081 in words is "twenty-one million, nine hundred nine thousand, eighty-one".