1812193921 has 4 divisors (see below), whose sum is σ = 1812279744. Its totient is φ = 1812108100.

The previous prime is 1812193883. The next prime is 1812193927. The reversal of 1812193921 is 1293912181.

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 a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 1812193921 - 2⁷ = 1812193793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1812193927) 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, 13356 + ... + 61666.

It is an arithmetic number, because the mean of its divisors is an integer number (453069936).

Almost surely, 2^1812193921 is an apocalyptic number.

It is an amenable number.

1812193921 is a deficient number, since it is larger than the sum of its proper divisors (85823).

1812193921 is an equidigital number, since it uses as much as digits as its factorization.

1812193921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 85822.

The product of its digits is 7776, while the sum is 37.

The square root of 1812193921 is about 42569.8710474909. The cubic root of 1812193921 is about 1219.1811043603.

The spelling of 1812193921 in words is "one billion, eight hundred twelve million, one hundred ninety-three thousand, nine hundred twenty-one".