21535109 has 4 divisors (see below), whose sum is σ = 21549420. Its totient is φ = 21520800.

The previous prime is 21535093. The next prime is 21535121. The reversal of 21535109 is 90153512.

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 5654884 + 15880225 = 2378^2 + 3985^2 .

It is a cyclic number.

It is not a de Polignac number, because 21535109 - 2⁴ = 21535093 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 (21535169) 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, 4592 + ... + 8009.

It is an arithmetic number, because the mean of its divisors is an integer number (5387355).

Almost surely, 2^21535109 is an apocalyptic number.

It is an amenable number.

21535109 is a deficient number, since it is larger than the sum of its proper divisors (14311).

21535109 is a wasteful number, since it uses less digits than its factorization.

21535109 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14310.

The product of its (nonzero) digits is 1350, while the sum is 26.

The square root of 21535109 is about 4640.5936042709. The cubic root of 21535109 is about 278.2161638448.

The spelling of 21535109 in words is "twenty-one million, five hundred thirty-five thousand, one hundred nine".