21008853 has 6 divisors (see below), whose sum is σ = 30346134. Its totient is φ = 14005896.

The previous prime is 21008849. The next prime is 21008857. The reversal of 21008853 is 35880012.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21008849) and next prime (21008857).

It can be written as a sum of positive squares in only one way, i.e., 17918289 + 3090564 = 4233^2 + 1758^2 .

It is not a de Polignac number, because 21008853 - 2² = 21008849 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21008857) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1167150 + ... + 1167167.

It is an arithmetic number, because the mean of its divisors is an integer number (5057689).

Almost surely, 2^21008853 is an apocalyptic number.

It is an amenable number.

21008853 is a deficient number, since it is larger than the sum of its proper divisors (9337281).

21008853 is a wasteful number, since it uses less digits than its factorization.

21008853 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2334323 (or 2334320 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 27.

The square root of 21008853 is about 4583.5415346651. The cubic root of 21008853 is about 275.9311816449.

Adding to 21008853 its reverse (35880012), we get a palindrome (56888865).

The spelling of 21008853 in words is "twenty-one million, eight thousand, eight hundred fifty-three".