1681399 has 4 divisors (see below), whose sum is σ = 1685920. Its totient is φ = 1676880.

The previous prime is 1681397. The next prime is 1681403. The reversal of 1681399 is 9931861.

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 1681399 - 2¹ = 1681397 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 (1681397) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1647 + ... + 2464.

It is an arithmetic number, because the mean of its divisors is an integer number (421480).

2^1681399 is an apocalyptic number.

1681399 is a deficient number, since it is larger than the sum of its proper divisors (4521).

1681399 is an equidigital number, since it uses as much as digits as its factorization.

1681399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4520.

The product of its digits is 11664, while the sum is 37.

The square root of 1681399 is about 1296.6877033426. The cubic root of 1681399 is about 118.9114281015.

It can be divided in two parts, 1681 and 399, that added together give a triangular number (2080 = T₆₄).

The spelling of 1681399 in words is "one million, six hundred eighty-one thousand, three hundred ninety-nine".