221688684 has 96 divisors (see below), whose sum is σ = 664957440. Its totient is φ = 62558784.

The previous prime is 221688683. The next prime is 221688689. The reversal of 221688684 is 486886122.

It is a super-2 number, since 2×221688684² = 98291745227303712, which contains 22 as substring.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (221688683) 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, 60982 + ... + 64514.

It is an arithmetic number, because the mean of its divisors is an integer number (6926640).

Almost surely, 2^221688684 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 221688684, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (332478720).

221688684 is an abundant number, since it is smaller than the sum of its proper divisors (443268756).

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

221688684 is a wasteful number, since it uses less digits than its factorization.

221688684 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3636 (or 3628 counting only the distinct ones).

The product of its digits is 294912, while the sum is 45.

The square root of 221688684 is about 14889.2136797079. The cubic root of 221688684 is about 605.2217241635.

The spelling of 221688684 in words is "two hundred twenty-one million, six hundred eighty-eight thousand, six hundred eighty-four".