221191820 has 24 divisors (see below), whose sum is σ = 479488128. Its totient is φ = 85622400.

The previous prime is 221191813. The next prime is 221191829. The reversal of 221191820 is 28191122.

221191820 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is a self number, because there is not a number n which added to its sum of digits gives 221191820.

It is not an unprimeable number, because it can be changed into a prime (221191829) 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, 177761 + ... + 179000.

It is an arithmetic number, because the mean of its divisors is an integer number (19978672).

Almost surely, 2^221191820 is an apocalyptic number.

221191820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

221191820 is an abundant number, since it is smaller than the sum of its proper divisors (258296308).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

221191820 is a wasteful number, since it uses less digits than its factorization.

221191820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 356801 (or 356799 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 26.

The square root of 221191820 is about 14872.5189527531. The cubic root of 221191820 is about 604.7692310231.

The spelling of 221191820 in words is "two hundred twenty-one million, one hundred ninety-one thousand, eight hundred twenty".