1819981 has 4 divisors (see below), whose sum is σ = 1858752. Its totient is φ = 1781212.

The previous prime is 1819957. The next prime is 1819999. The reversal of 1819981 is 1899181.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1819981 - 2¹⁷ = 1688909 is a prime.

It is a super-2 number, since 2×1819981² = 6624661680722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1819981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1819931) 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, 19315 + ... + 19408.

It is an arithmetic number, because the mean of its divisors is an integer number (464688).

2^1819981 is an apocalyptic number.

It is an amenable number.

1819981 is a deficient number, since it is larger than the sum of its proper divisors (38771).

1819981 is an equidigital number, since it uses as much as digits as its factorization.

1819981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38770.

The product of its digits is 5184, while the sum is 37.

The square root of 1819981 is about 1349.0667144363. The cubic root of 1819981 is about 122.0924901077.

The spelling of 1819981 in words is "one million, eight hundred nineteen thousand, nine hundred eighty-one".