221821740 has 240 divisors, whose sum is σ = 822226944. Its totient is φ = 48988800.

The previous prime is 221821739. The next prime is 221821741. The reversal of 221821740 is 47128122.

It is an interprime number because it is at equal distance from previous prime (221821739) and next prime (221821741).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (221821741) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 351225 + ... + 351855.

Almost surely, 2^221821740 is an apocalyptic number.

221821740 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 221821740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (411113472).

221821740 is an abundant number, since it is smaller than the sum of its proper divisors (600405204).

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

221821740 is a wasteful number, since it uses less digits than its factorization.

221821740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 690 (or 679 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 27.

The square root of 221821740 is about 14893.6812105000. The cubic root of 221821740 is about 605.3427832312.

Adding to 221821740 its reverse (47128122), we get a palindrome (268949862).

The spelling of 221821740 in words is "two hundred twenty-one million, eight hundred twenty-one thousand, seven hundred forty".