661161720 has 64 divisors (see below), whose sum is σ = 2051892000. Its totient is φ = 170229248.

The previous prime is 661161719. The next prime is 661161731. The reversal of 661161720 is 27161166.

661161720 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 91515 + ... + 98474.

Almost surely, 2^661161720 is an apocalyptic number.

661161720 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

661161720 is an abundant number, since it is smaller than the sum of its proper divisors (1390730280).

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

661161720 is a wasteful number, since it uses less digits than its factorization.

661161720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 190032 (or 190028 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 30.

The square root of 661161720 is about 25713.0651615088. The cubic root of 661161720 is about 871.1693089319.

The spelling of 661161720 in words is "six hundred sixty-one million, one hundred sixty-one thousand, seven hundred twenty".