661218084 has 36 divisors (see below), whose sum is σ = 1673253036. Its totient is φ = 220163328.

The previous prime is 661218073. The next prime is 661218091. The reversal of 661218084 is 480812166.

It can be written as a sum of positive squares in 2 ways, for example, as 354267684 + 306950400 = 18822^2 + 17520^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 24672 + ... + 43944.

It is an arithmetic number, because the mean of its divisors is an integer number (46479251).

Almost surely, 2^661218084 is an apocalyptic number.

It is an amenable number.

661218084 is an abundant number, since it is smaller than the sum of its proper divisors (1012034952).

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

661218084 is a wasteful number, since it uses less digits than its factorization.

661218084 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20236 (or 20231 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 36.

The square root of 661218084 is about 25714.1611568412. The cubic root of 661218084 is about 871.1940639402.

The spelling of 661218084 in words is "six hundred sixty-one million, two hundred eighteen thousand, eighty-four".