221721516 has 24 divisors (see below), whose sum is σ = 574833840. Its totient is φ = 73907136.

The previous prime is 221721509. The next prime is 221721551. The reversal of 221721516 is 615127122.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a self number, because there is not a number n which added to its sum of digits gives 221721516.

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, 1026381 + ... + 1026596.

It is an arithmetic number, because the mean of its divisors is an integer number (23951410).

Almost surely, 2^221721516 is an apocalyptic number.

It is an amenable number.

221721516 is an abundant number, since it is smaller than the sum of its proper divisors (353112324).

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

221721516 is a wasteful number, since it uses less digits than its factorization.

221721516 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2052990 (or 2052982 counting only the distinct ones).

The product of its digits is 1680, while the sum is 27.

The square root of 221721516 is about 14890.3161820023. The cubic root of 221721516 is about 605.2516003821.

Adding to 221721516 its reverse (615127122), we get a palindrome (836848638).

The spelling of 221721516 in words is "two hundred twenty-one million, seven hundred twenty-one thousand, five hundred sixteen".