21068509 has 8 divisors (see below), whose sum is σ = 26267328. Its totient is φ = 16416960.

The previous prime is 21068477. The next prime is 21068513. The reversal of 21068509 is 90586012.

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

It is not a de Polignac number, because 21068509 - 2⁵ = 21068477 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 (21068519) 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, 136732 + ... + 136885.

It is an arithmetic number, because the mean of its divisors is an integer number (3283416).

Almost surely, 2^21068509 is an apocalyptic number.

It is an amenable number.

21068509 is a deficient number, since it is larger than the sum of its proper divisors (5198819).

21068509 is a wasteful number, since it uses less digits than its factorization.

21068509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273635.

The product of its (nonzero) digits is 4320, while the sum is 31.

The square root of 21068509 is about 4590.0445531607. The cubic root of 21068509 is about 276.1921096524.

The spelling of 21068509 in words is "twenty-one million, sixty-eight thousand, five hundred nine".