660521820 has 192 divisors, whose sum is σ = 2230695936. Its totient is φ = 142771200.

The previous prime is 660521789. The next prime is 660521831. The reversal of 660521820 is 28125066.

It is a super-2 number, since 2×660521820² = 872578149392224800, which contains 22 as substring.

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 pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 975322 + ... + 975998.

It is an arithmetic number, because the mean of its divisors is an integer number (11618208).

Almost surely, 2^660521820 is an apocalyptic number.

660521820 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 660521820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1115347968).

660521820 is an abundant number, since it is smaller than the sum of its proper divisors (1570174116).

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

660521820 is a wasteful number, since it uses less digits than its factorization.

660521820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 820 (or 818 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 30.

The square root of 660521820 is about 25700.6190586920. The cubic root of 660521820 is about 870.8881668323. Note that the first 3 decimals are identical.

Adding to 660521820 its reverse (28125066), we get a palindrome (688646886).

The spelling of 660521820 in words is "six hundred sixty million, five hundred twenty-one thousand, eight hundred twenty".