661156660 has 12 divisors (see below), whose sum is σ = 1388429028. Its totient is φ = 264462656.

The previous prime is 661156649. The next prime is 661156681. The reversal of 661156660 is 66651166.

661156660 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 285339664 + 375816996 = 16892^2 + 19386^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16528897 + ... + 16528936.

It is an arithmetic number, because the mean of its divisors is an integer number (115702419).

Almost surely, 2^661156660 is an apocalyptic number.

It is an amenable number.

661156660 is an abundant number, since it is smaller than the sum of its proper divisors (727272368).

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

661156660 is a wasteful number, since it uses less digits than its factorization.

661156660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 33057842 (or 33057840 counting only the distinct ones).

The product of its (nonzero) digits is 38880, while the sum is 37.

The square root of 661156660 is about 25712.9667677614. The cubic root of 661156660 is about 871.1670865165.

The spelling of 661156660 in words is "six hundred sixty-one million, one hundred fifty-six thousand, six hundred sixty".