1666440 has 64 divisors (see below), whose sum is σ = 5558400. Its totient is φ = 444096.

The previous prime is 1666429. The next prime is 1666447. The reversal of 1666440 is 446661.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (1666447) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 309 + ... + 1851.

It is an arithmetic number, because the mean of its divisors is an integer number (86850).

2^1666440 is an apocalyptic number.

1666440 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 1666440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2779200).

1666440 is an abundant number, since it is smaller than the sum of its proper divisors (3891960).

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

1666440 is a wasteful number, since it uses less digits than its factorization.

1666440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1563 (or 1553 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 1666440 is about 1290.9066581283. The cubic root of 1666440 is about 118.5577350450.

The spelling of 1666440 in words is "one million, six hundred sixty-six thousand, four hundred forty".