661285920 has 48 divisors (see below), whose sum is σ = 2083052160. Its totient is φ = 176342784.

The previous prime is 661285909. The next prime is 661285939. The reversal of 661285920 is 29582166.

It is a tau number, because it is divible by the number of its divisors (48).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 688360 + ... + 689319.

It is an arithmetic number, because the mean of its divisors is an integer number (43396920).

Almost surely, 2^661285920 is an apocalyptic number.

661285920 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

661285920 is an abundant number, since it is smaller than the sum of its proper divisors (1421766240).

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

661285920 is a wasteful number, since it uses less digits than its factorization.

661285920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1377697 (or 1377689 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 39.

The square root of 661285920 is about 25715.4801627347. The cubic root of 661285920 is about 871.2238555733.

The spelling of 661285920 in words is "six hundred sixty-one million, two hundred eighty-five thousand, nine hundred twenty".