18781821 has 48 divisors (see below), whose sum is σ = 30945600. Its totient is φ = 11241216.

The previous prime is 18781801. The next prime is 18781831. The reversal of 18781821 is 12818781.

It is not a de Polignac number, because 18781821 - 2⁶ = 18781757 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18781801) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 226246 + ... + 226328.

It is an arithmetic number, because the mean of its divisors is an integer number (644700).

Almost surely, 2^18781821 is an apocalyptic number.

It is an amenable number.

18781821 is a deficient number, since it is larger than the sum of its proper divisors (12163779).

18781821 is a wasteful number, since it uses less digits than its factorization.

18781821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 155 (or 132 counting only the distinct ones).

The product of its digits is 7168, while the sum is 36.

The square root of 18781821 is about 4333.7998338640. The cubic root of 18781821 is about 265.8148456159.

The spelling of 18781821 in words is "eighteen million, seven hundred eighty-one thousand, eight hundred twenty-one".