221155221 has 8 divisors (see below), whose sum is σ = 336998464. Its totient is φ = 126374400.

The previous prime is 221155211. The next prime is 221155237. The reversal of 221155221 is 122551122.

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

It is not a de Polignac number, because 221155221 - 2⁶ = 221155157 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 10531201 = 221155221 / (2 + 2 + 1 + 1 + 5 + 5 + 2 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221155211) 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, 5265580 + ... + 5265621.

It is an arithmetic number, because the mean of its divisors is an integer number (42124808).

Almost surely, 2^221155221 is an apocalyptic number.

221155221 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

221155221 is a deficient number, since it is larger than the sum of its proper divisors (115843243).

221155221 is a wasteful number, since it uses less digits than its factorization.

221155221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10531211.

The product of its digits is 400, while the sum is 21.

The square root of 221155221 is about 14871.2884781380. The cubic root of 221155221 is about 604.7358735961.

The spelling of 221155221 in words is "two hundred twenty-one million, one hundred fifty-five thousand, two hundred twenty-one".