221666400 has 216 divisors, whose sum is σ = 828087624. Its totient is φ = 55603200.

The previous prime is 221666381. The next prime is 221666413. The reversal of 221666400 is 4666122.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 121495 + ... + 123305.

It is an arithmetic number, because the mean of its divisors is an integer number (3833739).

Almost surely, 2^221666400 is an apocalyptic number.

221666400 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 221666400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (414043812).

221666400 is an abundant number, since it is smaller than the sum of its proper divisors (606421224).

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

221666400 is a wasteful number, since it uses less digits than its factorization.

221666400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1854 (or 1838 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 221666400 is about 14888.4653339422. The cubic root of 221666400 is about 605.2014446547.

The spelling of 221666400 in words is "two hundred twenty-one million, six hundred sixty-six thousand, four hundred".