1620 has 30 divisors (see below), whose sum is σ = 5082. Its totient is φ = 432.

The previous prime is 1619. The next prime is 1621. The reversal of 1620 is 261.

1620 = T_{16} + T_{17} + ... +
T_{23}.

1620 is an esthetic number in base 16, because in such base its adjacent digits differ by 1.

It is an interprime number because it is at equal distance from previous prime (1619) and next prime (1621).

It can be written as a sum of positive squares in only one way, i.e., 1296 + 324 = 36^2 + 18^2 .

It is a tau number, because it is divible by the number of its divisors (30).

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a nialpdrome in base 9, base 12, base 15 and base 16.

It is a zygodrome in base 9.

It is a Saint-Exupery number, since it is equal to the product of the sides of a Pythagorean triangle: 15 × 9 × 12.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1621) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 322 + ... + 326.

1620 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1620, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2541).

1620 is an abundant number, since it is smaller than the sum of its proper divisors (3462).

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

1620 is a wasteful number, since it uses less digits than its factorization.

1620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21 (or 10 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 9.

The square root of 1620 is about 40.2492235950. The cubic root of 1620 is about 11.7446029235.

Adding to 1620 its reverse (261), we get a palindrome (1881).

It can be divided in two parts, 16 and 20, that added together give a triangular number (36 = T_{8}).

The spelling of 1620 in words is "one thousand, six hundred twenty".

Divisors: 1 2 3 4 5 6 9 10 12 15 18 20 27 30 36 45 54 60 81 90 108 135 162 180 270 324 405 540 810 1620

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