18021861 has 72 divisors (see below), whose sum is σ = 32920160. Its totient is φ = 9408960.

The previous prime is 18021841. The next prime is 18021889. The reversal of 18021861 is 16812081.

It is not a de Polignac number, because 18021861 - 2⁶ = 18021797 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18021841) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 268950 + ... + 269016.

Almost surely, 2^18021861 is an apocalyptic number.

18021861 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18021861 is a deficient number, since it is larger than the sum of its proper divisors (14898299).

18021861 is a wasteful number, since it uses less digits than its factorization.

18021861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127 (or 113 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 27.

The square root of 18021861 is about 4245.2162489089. The cubic root of 18021861 is about 262.1801928460.

It can be divided in two parts, 1802 and 1861, that added together give a palindrome (3663).

The spelling of 18021861 in words is "eighteen million, twenty-one thousand, eight hundred sixty-one".