1821001 has 8 divisors (see below), whose sum is σ = 2241344. Its totient is φ = 1440720.

The previous prime is 1820999. The next prime is 1821013. The reversal of 1821001 is 1001281.

1821001 = 94² + 95² + ... + 184².

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1821001 - 2¹ = 1820999 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (13).

1821001 is a modest number, since divided by 1001 gives 182 as remainder.

It is not an unprimeable number, because it can be changed into a prime (1821101) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9915 + ... + 10096.

It is an arithmetic number, because the mean of its divisors is an integer number (280168).

2^1821001 is an apocalyptic number.

It is an amenable number.

1821001 is a deficient number, since it is larger than the sum of its proper divisors (420343).

1821001 is a wasteful number, since it uses less digits than its factorization.

1821001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20031.

The product of its (nonzero) digits is 16, while the sum is 13.

The square root of 1821001 is about 1349.4447006084. Note that the first 3 decimals coincide. The cubic root of 1821001 is about 122.1152945733.

Adding to 1821001 its reverse (1001281), we get a palindrome (2822282).

The spelling of 1821001 in words is "one million, eight hundred twenty-one thousand, one".