1661645 has 8 divisors (see below), whose sum is σ = 2099040. Its totient is φ = 1259280.

The previous prime is 1661641. The next prime is 1661659. The reversal of 1661645 is 5461661.

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

It is not a de Polignac number, because 1661645 - 2² = 1661641 is a prime.

It is a super-3 number, since 3×1661645³ = 13763725099367733375, which contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8651 + ... + 8840.

It is an arithmetic number, because the mean of its divisors is an integer number (262380).

2^1661645 is an apocalyptic number.

It is an amenable number.

1661645 is a deficient number, since it is larger than the sum of its proper divisors (437395).

1661645 is a wasteful number, since it uses less digits than its factorization.

1661645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17515.

The product of its digits is 4320, while the sum is 29.

The square root of 1661645 is about 1289.0480984044. The cubic root of 1661645 is about 118.4439134726.

It can be divided in two parts, 16616 and 45, that added together give a palindrome (16661).

The spelling of 1661645 in words is "one million, six hundred sixty-one thousand, six hundred forty-five".