21016215 has 24 divisors (see below), whose sum is σ = 39740688. Its totient is φ = 10189440.

The previous prime is 21016201. The next prime is 21016217. The reversal of 21016215 is 51261012.

It is not a de Polignac number, because 21016215 - 2⁹ = 21015703 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21016217) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 20734 + ... + 21723.

It is an arithmetic number, because the mean of its divisors is an integer number (1655862).

Almost surely, 2^21016215 is an apocalyptic number.

21016215 is a deficient number, since it is larger than the sum of its proper divisors (18724473).

21016215 is a wasteful number, since it uses less digits than its factorization.

21016215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42479 (or 42476 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

The square root of 21016215 is about 4584.3445551136. The cubic root of 21016215 is about 275.9634088227.

Adding to 21016215 its reverse (51261012), we get a palindrome (72277227).

The spelling of 21016215 in words is "twenty-one million, sixteen thousand, two hundred fifteen".