221545355723721 has 10 divisors (see below), whose sum is σ = 330950469661482. Its totient is φ = 147696903815760.

The previous prime is 221545355723711. The next prime is 221545355723729. The reversal of 221545355723721 is 127327553545122.

221545355723721 is a `hidden beast` number, since 2 + 2 + 1 + 5 + 4 + 5 + 35 + 572 + 37 + 2 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 202025430009225 + 19519925714496 = 14213565^2 + 4418136^2 .

It is not a de Polignac number, because 221545355723721 - 2⁵ = 221545355723689 is a prime.

It is not an unprimeable number, because it can be changed into a prime (221545355723729) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 1367563924140 + ... + 1367563924301.

Almost surely, 2^{221545355723721} is an apocalyptic number.

It is an amenable number.

221545355723721 is a deficient number, since it is larger than the sum of its proper divisors (109405113937761).

221545355723721 is an equidigital number, since it uses as much as digits as its factorization.

221545355723721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2735127848453 (or 2735127848444 counting only the distinct ones).

The product of its digits is 17640000, while the sum is 54.

The spelling of 221545355723721 in words is "two hundred twenty-one trillion, five hundred forty-five billion, three hundred fifty-five million, seven hundred twenty-three thousand, seven hundred twenty-one".