21053509 has 8 divisors (see below), whose sum is σ = 21715200. Its totient is φ = 20400816.

The previous prime is 21053503. The next prime is 21053521. The reversal of 21053509 is 90535012.

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 21053509 - 2⁷ = 21053381 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 (21053503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2667 + ... + 7015.

It is an arithmetic number, because the mean of its divisors is an integer number (2714400).

Almost surely, 2^21053509 is an apocalyptic number.

It is an amenable number.

21053509 is a deficient number, since it is larger than the sum of its proper divisors (661691).

21053509 is a wasteful number, since it uses less digits than its factorization.

21053509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4499.

The product of its (nonzero) digits is 1350, while the sum is 25.

The square root of 21053509 is about 4588.4102911575. The cubic root of 21053509 is about 276.1265478982.

The spelling of 21053509 in words is "twenty-one million, fifty-three thousand, five hundred nine".