65561220 has 72 divisors (see below), whose sum is σ = 199554264. Its totient is φ = 17422848.

The previous prime is 65561219. The next prime is 65561239. The reversal of 65561220 is 2216556.

65561220 is a `hidden beast` number, since 655 + 6 + 1 + 2 + 2 + 0 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 16112196 + 49449024 = 4014^2 + 7032^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 81862 + ... + 82658.

It is an arithmetic number, because the mean of its divisors is an integer number (2771587).

Almost surely, 2^65561220 is an apocalyptic number.

65561220 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 65561220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (99777132).

65561220 is an abundant number, since it is smaller than the sum of its proper divisors (133993044).

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

65561220 is a wasteful number, since it uses less digits than its factorization.

65561220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1269 (or 1264 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 65561220 is about 8096.9883290023. The cubic root of 65561220 is about 403.2264467961.

Adding to 65561220 its reverse (2216556), we get a palindrome (67777776).

It can be divided in two parts, 6556 and 1220, that added together give a 5-th power (7776 = 6⁵).

The spelling of 65561220 in words is "sixty-five million, five hundred sixty-one thousand, two hundred twenty".