2221655721 has 16 divisors (see below), whose sum is σ = 3108094080. Its totient is φ = 1408872960.

The previous prime is 2221655717. The next prime is 2221655729. The reversal of 2221655721 is 1275561222.

It is not a de Polignac number, because 2221655721 - 2² = 2221655717 is a prime.

It is not an unprimeable number, because it can be changed into a prime (2221655729) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 76456 + ... + 101433.

It is an arithmetic number, because the mean of its divisors is an integer number (194255880).

Almost surely, 2^2221655721 is an apocalyptic number.

It is an amenable number.

2221655721 is a deficient number, since it is larger than the sum of its proper divisors (886438359).

2221655721 is a wasteful number, since it uses less digits than its factorization.

2221655721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 178096.

The product of its digits is 16800, while the sum is 33.

The square root of 2221655721 is about 47134.4430432778. The cubic root of 2221655721 is about 1304.8449821003.

The spelling of 2221655721 in words is "two billion, two hundred twenty-one million, six hundred fifty-five thousand, seven hundred twenty-one".