21801853 has 4 divisors (see below), whose sum is σ = 22001980. Its totient is φ = 21601728.

The previous prime is 21801851. The next prime is 21801869. The reversal of 21801853 is 35810812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7941124 + 13860729 = 2818^2 + 3723^2 .

It is a cyclic number.

It is not a de Polignac number, because 21801853 - 2¹ = 21801851 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21801851) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 99900 + ... + 100117.

It is an arithmetic number, because the mean of its divisors is an integer number (5500495).

Almost surely, 2^21801853 is an apocalyptic number.

It is an amenable number.

21801853 is a deficient number, since it is larger than the sum of its proper divisors (200127).

21801853 is a wasteful number, since it uses less digits than its factorization.

21801853 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 200126.

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 21801853 is about 4669.2454422530. The cubic root of 21801853 is about 279.3601588808.

The spelling of 21801853 in words is "twenty-one million, eight hundred one thousand, eight hundred fifty-three".