221216520 has 128 divisors (see below), whose sum is σ = 761529600. Its totient is φ = 50359296.

The previous prime is 221216473. The next prime is 221216521. The reversal of 221216520 is 25612122.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (221216521) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 326422 + ... + 327098.

It is an arithmetic number, because the mean of its divisors is an integer number (5949450).

Almost surely, 2^221216520 is an apocalyptic number.

221216520 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 221216520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (380764800).

221216520 is an abundant number, since it is smaller than the sum of its proper divisors (540313080).

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

221216520 is a wasteful number, since it uses less digits than its factorization.

221216520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1087 (or 1083 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 221216520 is about 14873.3493201767. The cubic root of 221216520 is about 604.7917412648.

Adding to 221216520 its reverse (25612122), we get a palindrome (246828642).

The spelling of 221216520 in words is "two hundred twenty-one million, two hundred sixteen thousand, five hundred twenty".