1664555640 has 128 divisors (see below), whose sum is σ = 5478520320. Its totient is φ = 401241600.

The previous prime is 1664555611. The next prime is 1664555681. The reversal of 1664555640 is 465554661.

1664555640 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is a junction number, because it is equal to n+sod(n) for n = 1664555592 and 1664555601.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 235437 + ... + 242403.

It is an arithmetic number, because the mean of its divisors is an integer number (42800940).

Almost surely, 2^1664555640 is an apocalyptic number.

1664555640 is a gapful number since it is divisible by the number (10) 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 1664555640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2739260160).

1664555640 is an abundant number, since it is smaller than the sum of its proper divisors (3813964680).

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

1664555640 is a wasteful number, since it uses less digits than its factorization.

1664555640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7173 (or 7169 counting only the distinct ones).

The product of its (nonzero) digits is 432000, while the sum is 42.

The square root of 1664555640 is about 40798.9661633723. The cubic root of 1664555640 is about 1185.1303102260.

The spelling of 1664555640 in words is "one billion, six hundred sixty-four million, five hundred fifty-five thousand, six hundred forty".