221421255546665 has 4 divisors (see below), whose sum is σ = 265705506656004. Its totient is φ = 177137004437328.

The previous prime is 221421255546649. The next prime is 221421255546679. The reversal of 221421255546665 is 566645552124122.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 48711089124889 + 172710166421776 = 6979333^2 + 13141924^2 .

It is a cyclic number.

It is not a de Polignac number, because 221421255546665 - 2⁴ = 221421255546649 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 221421255546665.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22142125554662 + ... + 22142125554671.

It is an arithmetic number, because the mean of its divisors is an integer number (66426376664001).

Almost surely, 2^{221421255546665} is an apocalyptic number.

It is an amenable number.

221421255546665 is a deficient number, since it is larger than the sum of its proper divisors (44284251109339).

221421255546665 is an equidigital number, since it uses as much as digits as its factorization.

221421255546665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44284251109338.

The product of its digits is 34560000, while the sum is 56.

The spelling of 221421255546665 in words is "two hundred twenty-one trillion, four hundred twenty-one billion, two hundred fifty-five million, five hundred forty-six thousand, six hundred sixty-five".