661101220 has 48 divisors (see below), whose sum is σ = 1531596528. Its totient is φ = 238141440.

The previous prime is 661101209. The next prime is 661101223. The reversal of 661101220 is 22101166.

It can be written as a sum of positive squares in 8 ways, for example, as 19289664 + 641811556 = 4392^2 + 25334^2 .

It is not an unprimeable number, because it can be changed into a prime (661101223) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20349 + ... + 41668.

It is an arithmetic number, because the mean of its divisors is an integer number (31908261).

Almost surely, 2^661101220 is an apocalyptic number.

It is an amenable number.

661101220 is an abundant number, since it is smaller than the sum of its proper divisors (870495308).

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

661101220 is a wasteful number, since it uses less digits than its factorization.

661101220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62080 (or 62078 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 661101220 is about 25711.8886898649. Note that the first 3 decimals coincide. The cubic root of 661101220 is about 871.1427358312.

Adding to 661101220 its reverse (22101166), we get a palindrome (683202386).

The spelling of 661101220 in words is "six hundred sixty-one million, one hundred one thousand, two hundred twenty".