1666664640 has 224 divisors, whose sum is σ = 6135989760. Its totient is φ = 425069568.

The previous prime is 1666664567. The next prime is 1666664647. The reversal of 1666664640 is 464666661.

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

It is not an unprimeable number, because it can be changed into a prime (1666664647) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 194527 + ... + 202913.

Almost surely, 2^1666664640 is an apocalyptic number.

1666664640 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 1666664640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3067994880).

1666664640 is an abundant number, since it is smaller than the sum of its proper divisors (4469325120).

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

1666664640 is a wasteful number, since it uses less digits than its factorization.

1666664640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8436 (or 8420 counting only the distinct ones).

The product of its (nonzero) digits is 746496, while the sum is 45.

The square root of 1666664640 is about 40824.8042248827. The cubic root of 1666664640 is about 1185.6306209207.

The spelling of 1666664640 in words is "one billion, six hundred sixty-six million, six hundred sixty-four thousand, six hundred forty".