21023215 has 16 divisors (see below), whose sum is σ = 27277920. Its totient is φ = 15500160.

The previous prime is 21023213. The next prime is 21023257. The reversal of 21023215 is 51232012.

It is not a de Polignac number, because 21023215 - 2¹ = 21023213 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21023213) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 525 + ... + 6505.

It is an arithmetic number, because the mean of its divisors is an integer number (1704870).

Almost surely, 2^21023215 is an apocalyptic number.

21023215 is a deficient number, since it is larger than the sum of its proper divisors (6254705).

21023215 is a wasteful number, since it uses less digits than its factorization.

21023215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6042.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 21023215 is about 4585.1079594705. The cubic root of 21023215 is about 275.9940443649.

Adding to 21023215 its reverse (51232012), we get a palindrome (72255227).

The spelling of 21023215 in words is "twenty-one million, twenty-three thousand, two hundred fifteen".