661810220 has 24 divisors (see below), whose sum is σ = 1390982208. Its totient is φ = 264499200.

The previous prime is 661810207. The next prime is 661810267. The reversal of 661810220 is 22018166.

661810220 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a self number, because there is not a number n which added to its sum of digits gives 661810220.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11180 + ... + 38060.

It is an arithmetic number, because the mean of its divisors is an integer number (57957592).

Almost surely, 2^661810220 is an apocalyptic number.

It is an amenable number.

661810220 is an abundant number, since it is smaller than the sum of its proper divisors (729171988).

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

661810220 is a wasteful number, since it uses less digits than its factorization.

661810220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28121 (or 28119 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 26.

The square root of 661810220 is about 25725.6723916014. The cubic root of 661810220 is about 871.4540444557.

Adding to 661810220 its reverse (22018166), we get a palindrome (683828386).

The spelling of 661810220 in words is "six hundred sixty-one million, eight hundred ten thousand, two hundred twenty".