1820981 has 4 divisors (see below), whose sum is σ = 1839852. Its totient is φ = 1802112.

The previous prime is 1820977. The next prime is 1820983. The reversal of 1820981 is 1890281.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1500625 + 320356 = 1225^2 + 566^2 .

It is a cyclic number.

It is not a de Polignac number, because 1820981 - 2² = 1820977 is a prime.

It is a super-2 number, since 2×1820981² = 6631943604722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1820983) 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, 9290 + ... + 9483.

It is an arithmetic number, because the mean of its divisors is an integer number (459963).

2^1820981 is an apocalyptic number.

It is an amenable number.

1820981 is a deficient number, since it is larger than the sum of its proper divisors (18871).

1820981 is an equidigital number, since it uses as much as digits as its factorization.

1820981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18870.

The product of its (nonzero) digits is 1152, while the sum is 29.

The square root of 1820981 is about 1349.4372901324. The cubic root of 1820981 is about 122.1148475088.

The spelling of 1820981 in words is "one million, eight hundred twenty thousand, nine hundred eighty-one".