221015721 has 8 divisors (see below), whose sum is σ = 295563424. Its totient is φ = 146905920.

The previous prime is 221015713. The next prime is 221015731. The reversal of 221015721 is 127510122.

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

It is not a de Polignac number, because 221015721 - 2³ = 221015713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (221015731) 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, 108295 + ... + 110316.

It is an arithmetic number, because the mean of its divisors is an integer number (36945428).

Almost surely, 2^221015721 is an apocalyptic number.

It is an amenable number.

221015721 is a deficient number, since it is larger than the sum of its proper divisors (74547703).

221015721 is a wasteful number, since it uses less digits than its factorization.

221015721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 218951.

The product of its (nonzero) digits is 280, while the sum is 21.

The square root of 221015721 is about 14866.5974923652. The cubic root of 221015721 is about 604.6086953517.

Adding to 221015721 its reverse (127510122), we get a palindrome (348525843).

The spelling of 221015721 in words is "two hundred twenty-one million, fifteen thousand, seven hundred twenty-one".