21508853 has 4 divisors (see below), whose sum is σ = 21531180. Its totient is φ = 21486528.

The previous prime is 21508801. The next prime is 21508867. The reversal of 21508853 is 35880512.

It is a happy number.

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 16589329 + 4919524 = 4073^2 + 2218^2 .

It is a cyclic number.

It is not a de Polignac number, because 21508853 - 2⁶ = 21508789 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 (21508153) 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, 9650 + ... + 11667.

It is an arithmetic number, because the mean of its divisors is an integer number (5382795).

Almost surely, 2^21508853 is an apocalyptic number.

It is an amenable number.

21508853 is a deficient number, since it is larger than the sum of its proper divisors (22327).

21508853 is a wasteful number, since it uses less digits than its factorization.

21508853 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22326.

The product of its (nonzero) digits is 9600, while the sum is 32.

The square root of 21508853 is about 4637.7637930365. The cubic root of 21508853 is about 278.1030491113.

The spelling of 21508853 in words is "twenty-one million, five hundred eight thousand, eight hundred fifty-three".