21570216 has 32 divisors (see below), whose sum is σ = 54237600. Its totient is φ = 7148480.

The previous prime is 21570193. The next prime is 21570233. The reversal of 21570216 is 61207512.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1786 + ... + 6806.

It is an arithmetic number, because the mean of its divisors is an integer number (1694925).

Almost surely, 2^21570216 is an apocalyptic number.

It is an amenable number.

21570216 is an abundant number, since it is smaller than the sum of its proper divisors (32667384).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21570216 is a wasteful number, since it uses less digits than its factorization.

21570216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5209 (or 5205 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21570216 is about 4644.3746618894. The cubic root of 21570216 is about 278.3672664315.

Adding to 21570216 its reverse (61207512), we get a palindrome (82777728).

The spelling of 21570216 in words is "twenty-one million, five hundred seventy thousand, two hundred sixteen".