20491218 has 48 divisors (see below), whose sum is σ = 50240736. Its totient is φ = 6207840.

The previous prime is 20491193. The next prime is 20491223. The reversal of 20491218 is 81219402.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 20491191 and 20491200.

It is an unprimeable number.

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, 3430 + ... + 7262.

It is an arithmetic number, because the mean of its divisors is an integer number (1046682).

Almost surely, 2^20491218 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20491218, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25120368).

20491218 is an abundant number, since it is smaller than the sum of its proper divisors (29749518).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20491218 is a wasteful number, since it uses less digits than its factorization.

20491218 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3861 (or 3849 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 20491218 is about 4526.7226555202. The cubic root of 20491218 is about 273.6460968037.

The spelling of 20491218 in words is "twenty million, four hundred ninety-one thousand, two hundred eighteen".