661644288 has 132 divisors (see below), whose sum is σ = 1981987280. Its totient is φ = 220465152.

The previous prime is 661644287. The next prime is 661644299. The reversal of 661644288 is 882446166.

661644288 is a `hidden beast` number, since 6 + 616 + 4 + 4 + 28 + 8 = 666.

It is a nude number because it is divisible by every one of its digits.

It is not an unprimeable number, because it can be changed into a prime (661644287) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 247503 + ... + 250161.

Almost surely, 2^661644288 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661644288, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (990993640).

661644288 is an abundant number, since it is smaller than the sum of its proper divisors (1320342992).

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

661644288 is an equidigital number, since it uses as much as digits as its factorization.

661644288 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2694 (or 2664 counting only the distinct ones).

The product of its digits is 442368, while the sum is 45.

The square root of 661644288 is about 25722.4471619634. The cubic root of 661644288 is about 871.3812067575.

The spelling of 661644288 in words is "six hundred sixty-one million, six hundred forty-four thousand, two hundred eighty-eight".