1821000921 has 4 divisors (see below), whose sum is σ = 2428001232. Its totient is φ = 1214000612.

The previous prime is 1821000913. The next prime is 1821000943. The reversal of 1821000921 is 1290001281.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1290001281 = 3 ⋅430000427.

It is a cyclic number.

It is not a de Polignac number, because 1821000921 - 2³ = 1821000913 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1821000891 and 1821000900.

It is not an unprimeable number, because it can be changed into a prime (1821000221) 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, 303500151 + ... + 303500156.

It is an arithmetic number, because the mean of its divisors is an integer number (607000308).

Almost surely, 2^1821000921 is an apocalyptic number.

It is an amenable number.

1821000921 is a deficient number, since it is larger than the sum of its proper divisors (607000311).

1821000921 is an equidigital number, since it uses as much as digits as its factorization.

1821000921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 607000310.

The product of its (nonzero) digits is 288, while the sum is 24.

The square root of 1821000921 is about 42673.1873780246. The cubic root of 1821000921 is about 1221.1529280743.

The spelling of 1821000921 in words is "one billion, eight hundred twenty-one million, nine hundred twenty-one", and thus it is an aban number.