21801918 has 8 divisors (see below), whose sum is σ = 43603848. Its totient is φ = 7267304.

The previous prime is 21801893. The next prime is 21801929. The reversal of 21801918 is 81910812.

It is a sphenic number, since it is the product of 3 distinct primes.

21801918 is an admirable number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1816821 + ... + 1816832.

It is an arithmetic number, because the mean of its divisors is an integer number (5450481).

Almost surely, 2^21801918 is an apocalyptic number.

21801918 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21801918 is a wasteful number, since it uses less digits than its factorization.

21801918 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3633658.

The product of its (nonzero) digits is 1152, while the sum is 30.

The square root of 21801918 is about 4669.2524026872. The cubic root of 21801918 is about 279.3604365084.

The spelling of 21801918 in words is "twenty-one million, eight hundred one thousand, nine hundred eighteen".