1661405 has 8 divisors (see below), whose sum is σ = 2080512. Its totient is φ = 1271248.

The previous prime is 1661353. The next prime is 1661431. The reversal of 1661405 is 5041661.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1661405 - 2¹⁸ = 1399261 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 7109 + ... + 7338.

It is an arithmetic number, because the mean of its divisors is an integer number (260064).

2^1661405 is an apocalyptic number.

It is an amenable number.

1661405 is a deficient number, since it is larger than the sum of its proper divisors (419107).

1661405 is a wasteful number, since it uses less digits than its factorization.

1661405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14475.

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 1661405 is about 1288.9550030936. The cubic root of 1661405 is about 118.4382107086.

The spelling of 1661405 in words is "one million, six hundred sixty-one thousand, four hundred five".