1666535640 has 128 divisors (see below), whose sum is σ = 6233310720. Its totient is φ = 346291200.

The previous prime is 1666535621. The next prime is 1666535659. The reversal of 1666535640 is 465356661.

It is an interprime number because it is at equal distance from previous prime (1666535621) and next prime (1666535659).

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a junction number, because it is equal to n+sod(n) for n = 1666535592 and 1666535601.

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, 80941 + ... + 99420.

It is an arithmetic number, because the mean of its divisors is an integer number (48697740).

Almost surely, 2^1666535640 is an apocalyptic number.

1666535640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1666535640 is an abundant number, since it is smaller than the sum of its proper divisors (4566775080).

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

1666535640 is a wasteful number, since it uses less digits than its factorization.

1666535640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 180393 (or 180389 counting only the distinct ones).

The product of its (nonzero) digits is 388800, while the sum is 42.

The square root of 1666535640 is about 40823.2242724653. The cubic root of 1666535640 is about 1185.6000308242.

The spelling of 1666535640 in words is "one billion, six hundred sixty-six million, five hundred thirty-five thousand, six hundred forty".