221991900 has 72 divisors (see below), whose sum is σ = 691716144. Its totient is φ = 54643200.

The previous prime is 221991893. The next prime is 221991911. The reversal of 221991900 is 9199122.

It is a super-2 number, since 2×221991900² = 98560807331220000, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 24561 + ... + 32360.

Almost surely, 2^221991900 is an apocalyptic number.

221991900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

221991900 is an abundant number, since it is smaller than the sum of its proper divisors (469724244).

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

221991900 is a wasteful number, since it uses less digits than its factorization.

221991900 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56951 (or 56944 counting only the distinct ones).

The product of its (nonzero) digits is 2916, while the sum is 33.

The square root of 221991900 is about 14899.3926050695. The cubic root of 221991900 is about 605.4975303128.

The spelling of 221991900 in words is "two hundred twenty-one million, nine hundred ninety-one thousand, nine hundred".