1661015 has 4 divisors (see below), whose sum is σ = 1993224. Its totient is φ = 1328808.

The previous prime is 1661003. The next prime is 1661021. The reversal of 1661015 is 5101661.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1661015 - 2¹⁸ = 1398871 is a prime.

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 (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 166097 + ... + 166106.

It is an arithmetic number, because the mean of its divisors is an integer number (498306).

2^1661015 is an apocalyptic number.

1661015 is a deficient number, since it is larger than the sum of its proper divisors (332209).

1661015 is an equidigital number, since it uses as much as digits as its factorization.

1661015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 332208.

The product of its (nonzero) digits is 180, while the sum is 20.

The square root of 1661015 is about 1288.8037088711. The cubic root of 1661015 is about 118.4289425456.

Adding to 1661015 its reverse (5101661), we get a palindrome (6762676).

It can be divided in two parts, 166 and 1015, that multiplied together give a triangular number (168490 = T₅₈₀).

The spelling of 1661015 in words is "one million, six hundred sixty-one thousand, fifteen".