646221720 has 64 divisors (see below), whose sum is σ = 1953976320. Its totient is φ = 170964864.

The previous prime is 646221701. The next prime is 646221743. The reversal of 646221720 is 27122646.

It is a super-2 number, since 2×646221720² = 835205022799516800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30).

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 15 ways as a sum of consecutive naturals, for example, 5962 + ... + 36441.

It is an arithmetic number, because the mean of its divisors is an integer number (30530880).

Almost surely, 2^646221720 is an apocalyptic number.

646221720 is a gapful number since it is divisible by the number (60) 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 646221720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (976988160).

646221720 is an abundant number, since it is smaller than the sum of its proper divisors (1307754600).

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

646221720 is a wasteful number, since it uses less digits than its factorization.

646221720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42544 (or 42540 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 30.

The square root of 646221720 is about 25420.8914084459. The cubic root of 646221720 is about 864.5574356295.

It can be divided in two parts, 6462 and 21720, that added together give a palindrome (28182).

The spelling of 646221720 in words is "six hundred forty-six million, two hundred twenty-one thousand, seven hundred twenty".