1661440 has 80 divisors (see below), whose sum is σ = 4419360. Its totient is φ = 593920.

The previous prime is 1661437. The next prime is 1661441. The reversal of 1661440 is 441661.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (22).

It is not an unprimeable number, because it can be changed into a prime (1661441) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28131 + ... + 28189.

It is an arithmetic number, because the mean of its divisors is an integer number (55242).

2^1661440 is an apocalyptic number.

1661440 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 1661440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2209680).

1661440 is an abundant number, since it is smaller than the sum of its proper divisors (2757920).

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

1661440 is an equidigital number, since it uses as much as digits as its factorization.

1661440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93 (or 77 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 1661440 is about 1288.9685799119. The cubic root of 1661440 is about 118.4390423958.

The spelling of 1661440 in words is "one million, six hundred sixty-one thousand, four hundred forty".