1581681 has 8 divisors (see below), whose sum is σ = 2124640. Its totient is φ = 1046592.

The previous prime is 1581673. The next prime is 1581707. The reversal of 1581681 is 1861851.

It is a happy number.

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

It is not a de Polignac number, because 1581681 - 2³ = 1581673 is a prime.

It is a super-2 number, since 2×1581681² = 5003429571522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1581611) 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, 1480 + ... + 2313.

It is an arithmetic number, because the mean of its divisors is an integer number (265580).

2^1581681 is an apocalyptic number.

It is an amenable number.

1581681 is a deficient number, since it is larger than the sum of its proper divisors (542959).

1581681 is a wasteful number, since it uses less digits than its factorization.

1581681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3935.

The product of its digits is 1920, while the sum is 30.

The square root of 1581681 is about 1257.6489971371. The cubic root of 1581681 is about 116.5126193604.

The spelling of 1581681 in words is "one million, five hundred eighty-one thousand, six hundred eighty-one".