21015853 has 8 divisors (see below), whose sum is σ = 21340800. Its totient is φ = 20693568.

The previous prime is 21015851. The next prime is 21015857. The reversal of 21015853 is 35851012.

It is a happy number.

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 21015853 - 2¹ = 21015851 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 (21015851) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19708 + ... + 20746.

It is an arithmetic number, because the mean of its divisors is an integer number (2667600).

Almost surely, 2^21015853 is an apocalyptic number.

It is an amenable number.

21015853 is a deficient number, since it is larger than the sum of its proper divisors (324947).

21015853 is a wasteful number, since it uses less digits than its factorization.

21015853 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1331.

The product of its (nonzero) digits is 1200, while the sum is 25.

The square root of 21015853 is about 4584.3050727455. The cubic root of 21015853 is about 275.9618243425.

Adding to 21015853 its reverse (35851012), we get a palindrome (56866865).

The spelling of 21015853 in words is "twenty-one million, fifteen thousand, eight hundred fifty-three".