21210215 has 16 divisors (see below), whose sum is σ = 27604416. Its totient is φ = 15552000.

The previous prime is 21210197. The next prime is 21210221. The reversal of 21210215 is 51201212.

It is not a de Polignac number, because 21210215 - 2⁶ = 21210151 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21210215.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8735 + ... + 10895.

It is an arithmetic number, because the mean of its divisors is an integer number (1725276).

Almost surely, 2^21210215 is an apocalyptic number.

21210215 is a deficient number, since it is larger than the sum of its proper divisors (6394201).

21210215 is a wasteful number, since it uses less digits than its factorization.

21210215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2330.

The product of its (nonzero) digits is 40, while the sum is 14.

The square root of 21210215 is about 4605.4549178121. The cubic root of 21210215 is about 276.8099457860.

Adding to 21210215 its reverse (51201212), we get a palindrome (72411427).

The spelling of 21210215 in words is "twenty-one million, two hundred ten thousand, two hundred fifteen".