1815661 has 8 divisors (see below), whose sum is σ = 1896120. Its totient is φ = 1736448.

The previous prime is 1815647. The next prime is 1815673. The reversal of 1815661 is 1665181.

It can be written as a sum of positive squares in 4 ways, for example, as 670761 + 1144900 = 819^2 + 1070^2 .

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 1815661 - 2⁵ = 1815629 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1815631) by changing a digit.

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, 3745 + ... + 4201.

It is an arithmetic number, because the mean of its divisors is an integer number (237015).

2^1815661 is an apocalyptic number.

It is an amenable number.

1815661 is a deficient number, since it is larger than the sum of its proper divisors (80459).

1815661 is a wasteful number, since it uses less digits than its factorization.

1815661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 623.

The product of its digits is 1440, while the sum is 28.

The square root of 1815661 is about 1347.4646563083. The cubic root of 1815661 is about 121.9958119139.

The spelling of 1815661 in words is "one million, eight hundred fifteen thousand, six hundred sixty-one".