661495680 has 128 divisors (see below), whose sum is σ = 2342858400. Its totient is φ = 176394240.

The previous prime is 661495673. The next prime is 661495699. The reversal of 661495680 is 86594166.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (45).

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, 1861 + ... + 36420.

Almost surely, 2^661495680 is an apocalyptic number.

661495680 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 661495680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1171429200).

661495680 is an abundant number, since it is smaller than the sum of its proper divisors (1681362720).

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

661495680 is a wasteful number, since it uses less digits than its factorization.

661495680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38309 (or 38291 counting only the distinct ones).

The product of its (nonzero) digits is 311040, while the sum is 45.

The square root of 661495680 is about 25719.5583165808. The cubic root of 661495680 is about 871.3159632841.

The spelling of 661495680 in words is "six hundred sixty-one million, four hundred ninety-five thousand, six hundred eighty".