221728906978 has 8 divisors (see below), whose sum is σ = 332595417168. Its totient is φ = 110863767924.

The previous prime is 221728906967. The next prime is 221728906979. The reversal of 221728906978 is 879609827122.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (221728906979) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 310525 + ... + 734767.

It is an arithmetic number, because the mean of its divisors is an integer number (41574427146).

Almost surely, 2^221728906978 is an apocalyptic number.

221728906978 is a deficient number, since it is larger than the sum of its proper divisors (110866510190).

221728906978 is a wasteful number, since it uses less digits than its factorization.

221728906978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 685568.

The product of its (nonzero) digits is 12192768, while the sum is 61.

The spelling of 221728906978 in words is "two hundred twenty-one billion, seven hundred twenty-eight million, nine hundred six thousand, nine hundred seventy-eight".