221801866 has 16 divisors (see below), whose sum is σ = 390868128. Its totient is φ = 93063600.

The previous prime is 221801863. The next prime is 221801887. The reversal of 221801866 is 668108122.

221801866 is digitally balanced in base 2 and base 3, because in such bases it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×221801866² = 98392135522163912, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (221801861) 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, 387480 + ... + 388051.

It is an arithmetic number, because the mean of its divisors is an integer number (24429258).

Almost surely, 2^221801866 is an apocalyptic number.

221801866 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

221801866 is a deficient number, since it is larger than the sum of its proper divisors (169066262).

221801866 is a wasteful number, since it uses less digits than its factorization.

221801866 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 775557.

The product of its (nonzero) digits is 9216, while the sum is 34.

The square root of 221801866 is about 14893.0139998591. The cubic root of 221801866 is about 605.3247042371.

Adding to 221801866 its reverse (668108122), we get a palindrome (889909988).

The spelling of 221801866 in words is "two hundred twenty-one million, eight hundred one thousand, eight hundred sixty-six".