221891791 has 4 divisors (see below), whose sum is σ = 242063784. Its totient is φ = 201719800.

The previous prime is 221891783. The next prime is 221891807. The reversal of 221891791 is 197198122.

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

It is a cyclic number.

It is not a de Polignac number, because 221891791 - 2³ = 221891783 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (221891771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10085980 + ... + 10086001.

It is an arithmetic number, because the mean of its divisors is an integer number (60515946).

Almost surely, 2^221891791 is an apocalyptic number.

221891791 is a deficient number, since it is larger than the sum of its proper divisors (20171993).

221891791 is a wasteful number, since it uses less digits than its factorization.

221891791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20171992.

The product of its digits is 18144, while the sum is 40.

The square root of 221891791 is about 14896.0327268706. The cubic root of 221891791 is about 605.4064986637.

The spelling of 221891791 in words is "two hundred twenty-one million, eight hundred ninety-one thousand, seven hundred ninety-one".