1666391540 has 24 divisors (see below), whose sum is σ = 3817552032. Its totient is φ = 605960480.

The previous prime is 1666391537. The next prime is 1666391549. The reversal of 1666391540 is 451936661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1666391549) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3787034 + ... + 3787473.

It is an arithmetic number, because the mean of its divisors is an integer number (159064668).

Almost surely, 2^1666391540 is an apocalyptic number.

1666391540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1666391540 is an abundant number, since it is smaller than the sum of its proper divisors (2151160492).

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

1666391540 is a wasteful number, since it uses less digits than its factorization.

1666391540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7574527 (or 7574525 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 41.

The square root of 1666391540 is about 40821.4593075750. The cubic root of 1666391540 is about 1185.5658581599.

The spelling of 1666391540 in words is "one billion, six hundred sixty-six million, three hundred ninety-one thousand, five hundred forty".