661816320 has 176 divisors, whose sum is σ = 2309802048. Its totient is φ = 160399360.

The previous prime is 661816313. The next prime is 661816333. The reversal of 661816320 is 23618166.

It is a tau number, because it is divible by the number of its divisors (176).

It is a Harshad number since it is a multiple of its sum of digits (33).

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, 167002 + ... + 170918.

Almost surely, 2^661816320 is an apocalyptic number.

661816320 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 661816320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1154901024).

661816320 is an abundant number, since it is smaller than the sum of its proper divisors (1647985728).

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

661816320 is a wasteful number, since it uses less digits than its factorization.

661816320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3956 (or 3938 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 661816320 is about 25725.7909499397. The cubic root of 661816320 is about 871.4567218866.

The spelling of 661816320 in words is "six hundred sixty-one million, eight hundred sixteen thousand, three hundred twenty".