18721845 has 24 divisors (see below), whose sum is σ = 34361496. Its totient is φ = 9397248.

The previous prime is 18721841. The next prime is 18721847. The reversal of 18721845 is 54812781.

It can be written as a sum of positive squares in 4 ways, for example, as 6380676 + 12341169 = 2526^2 + 3513^2 .

It is not a de Polignac number, because 18721845 - 2² = 18721841 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18721841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 11472 + ... + 13001.

It is an arithmetic number, because the mean of its divisors is an integer number (1431729).

Almost surely, 2^18721845 is an apocalyptic number.

18721845 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

18721845 is a deficient number, since it is larger than the sum of its proper divisors (15639651).

18721845 is a wasteful number, since it uses less digits than its factorization.

18721845 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24501 (or 24498 counting only the distinct ones).

The product of its digits is 17920, while the sum is 36.

The square root of 18721845 is about 4326.8747381915. The cubic root of 18721845 is about 265.5316016732.

The spelling of 18721845 in words is "eighteen million, seven hundred twenty-one thousand, eight hundred forty-five".