1981665 has 48 divisors (see below), whose sum is σ = 4088448. Its totient is φ = 902016.

The previous prime is 1981663. The next prime is 1981667. The reversal of 1981665 is 5661891.

It is an interprime number because it is at equal distance from previous prime (1981663) and next prime (1981667).

It is not a de Polignac number, because 1981665 - 2¹ = 1981663 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1981663) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 8389 + ... + 8621.

It is an arithmetic number, because the mean of its divisors is an integer number (85176).

2^1981665 is an apocalyptic number.

1981665 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1981665 is an abundant number, since it is smaller than the sum of its proper divisors (2106783).

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

1981665 is an equidigital number, since it uses as much as digits as its factorization.

1981665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 260 (or 248 counting only the distinct ones).

The product of its digits is 12960, while the sum is 36.

The square root of 1981665 is about 1407.7162356100. The cubic root of 1981665 is about 125.6059115573.

It can be divided in two parts, 19816 and 65, that added together give a square (19881 = 141²).

The spelling of 1981665 in words is "one million, nine hundred eighty-one thousand, six hundred sixty-five".