21798018 has 32 divisors (see below), whose sum is σ = 52845120. Its totient is φ = 6605280.

The previous prime is 21798017. The next prime is 21798047. The reversal of 21798018 is 81089712.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21798017) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17755 + ... + 18942.

It is an arithmetic number, because the mean of its divisors is an integer number (1651410).

Almost surely, 2^21798018 is an apocalyptic number.

21798018 is an abundant number, since it is smaller than the sum of its proper divisors (31047102).

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

21798018 is a wasteful number, since it uses less digits than its factorization.

21798018 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36719 (or 36713 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 21798018 is about 4668.8347582668. The cubic root of 21798018 is about 279.3437778720.

The spelling of 21798018 in words is "twenty-one million, seven hundred ninety-eight thousand, eighteen".