21015385 has 8 divisors (see below), whose sum is σ = 25272000. Its totient is φ = 16776624.

The previous prime is 21015317. The next prime is 21015391. The reversal of 21015385 is 58351012.

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 21015385 - 2⁷ = 21015257 is a prime.

It is an unprimeable number.

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, 1717 + ... + 6706.

It is an arithmetic number, because the mean of its divisors is an integer number (3159000).

Almost surely, 2^21015385 is an apocalyptic number.

It is an amenable number.

21015385 is a deficient number, since it is larger than the sum of its proper divisors (4256615).

21015385 is an equidigital number, since it uses as much as digits as its factorization.

21015385 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8927.

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

The square root of 21015385 is about 4584.2540287379. The cubic root of 21015385 is about 275.9597758716.

Adding to 21015385 its reverse (58351012), we get a palindrome (79366397).

The spelling of 21015385 in words is "twenty-one million, fifteen thousand, three hundred eighty-five".