21308215 has 16 divisors (see below), whose sum is σ = 27364320. Its totient is φ = 15880320.

The previous prime is 21308213. The next prime is 21308219. The reversal of 21308215 is 51280312.

It is not a de Polignac number, because 21308215 - 2¹ = 21308213 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21308213) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3957 + ... + 7633.

It is an arithmetic number, because the mean of its divisors is an integer number (1710270).

Almost surely, 2^21308215 is an apocalyptic number.

21308215 is a deficient number, since it is larger than the sum of its proper divisors (6056105).

21308215 is a wasteful number, since it uses less digits than its factorization.

21308215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3762.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21308215 is about 4616.0822133060. The cubic root of 21308215 is about 277.2356164937.

Adding to 21308215 its reverse (51280312), we get a palindrome (72588527).

The spelling of 21308215 in words is "twenty-one million, three hundred eight thousand, two hundred fifteen".