1661355 has 12 divisors (see below), whose sum is σ = 2879760. Its totient is φ = 886032.

The previous prime is 1661353. The next prime is 1661431. The reversal of 1661355 is 5531661.

It is a happy number.

It is not a de Polignac number, because 1661355 - 2¹ = 1661353 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1661353) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18415 + ... + 18504.

It is an arithmetic number, because the mean of its divisors is an integer number (239980).

2^1661355 is an apocalyptic number.

1661355 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

1661355 is a deficient number, since it is larger than the sum of its proper divisors (1218405).

1661355 is a wasteful number, since it uses less digits than its factorization.

1661355 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36930 (or 36927 counting only the distinct ones).

The product of its digits is 2700, while the sum is 27.

The square root of 1661355 is about 1288.9356073908. The cubic root of 1661355 is about 118.4370225636.

It can be divided in two parts, 1661 and 355, that added together give a triangular number (2016 = T₆₃).

The spelling of 1661355 in words is "one million, six hundred sixty-one thousand, three hundred fifty-five".