221681778 has 16 divisors (see below), whose sum is σ = 466698720. Its totient is φ = 70004736.

The previous prime is 221681777. The next prime is 221681791. The reversal of 221681778 is 877186122.

221681778 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not an unprimeable number, because it can be changed into a prime (221681773) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 972175 + ... + 972402.

It is an arithmetic number, because the mean of its divisors is an integer number (29168670).

Almost surely, 2^221681778 is an apocalyptic number.

221681778 is an abundant number, since it is smaller than the sum of its proper divisors (245016942).

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

221681778 is a wasteful number, since it uses less digits than its factorization.

221681778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1944601.

The product of its digits is 75264, while the sum is 42.

The square root of 221681778 is about 14888.9817650503. The cubic root of 221681778 is about 605.2154395176.

The spelling of 221681778 in words is "two hundred twenty-one million, six hundred eighty-one thousand, seven hundred seventy-eight".