1681561 has 8 divisors (see below), whose sum is σ = 1931904. Its totient is φ = 1433760.

The previous prime is 1681541. The next prime is 1681571. The reversal of 1681561 is 1651861.

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 1681561 - 2¹⁵ = 1648793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1681501) 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, 1116 + ... + 2146.

It is an arithmetic number, because the mean of its divisors is an integer number (241488).

2^1681561 is an apocalyptic number.

It is an amenable number.

1681561 is a deficient number, since it is larger than the sum of its proper divisors (250343).

1681561 is a wasteful number, since it uses less digits than its factorization.

1681561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1271.

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

The square root of 1681561 is about 1296.7501686909. The cubic root of 1681561 is about 118.9152469517.

The spelling of 1681561 in words is "one million, six hundred eighty-one thousand, five hundred sixty-one".