1681720 has 16 divisors (see below), whose sum is σ = 3783960. Its totient is φ = 672672.

The previous prime is 1681717. The next prime is 1681721. The reversal of 1681720 is 271861.

It is a plaindrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1681721) 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, 20982 + ... + 21061.

2^1681720 is an apocalyptic number.

1681720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1681720 is an abundant number, since it is smaller than the sum of its proper divisors (2102240).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1681720 is a wasteful number, since it uses less digits than its factorization.

1681720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42054 (or 42050 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 25.

The square root of 1681720 is about 1296.8114743478. The cubic root of 1681720 is about 118.9189948440.

It can be divided in two parts, 1681 and 720, that added together give a 4-th power (2401 = 7⁴).

The spelling of 1681720 in words is "one million, six hundred eighty-one thousand, seven hundred twenty".