21850121 has 4 divisors (see below), whose sum is σ = 21860244. Its totient is φ = 21840000.

The previous prime is 21850099. The next prime is 21850177. The reversal of 21850121 is 12105812.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 2805625 + 19044496 = 1675^2 + 4364^2 .

It is a cyclic number.

It is not a de Polignac number, because 21850121 - 2²² = 17655817 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21850093 and 21850102.

It is not an unprimeable number, because it can be changed into a prime (21850181) 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, 380 + ... + 6621.

It is an arithmetic number, because the mean of its divisors is an integer number (5465061).

Almost surely, 2^21850121 is an apocalyptic number.

It is an amenable number.

21850121 is a deficient number, since it is larger than the sum of its proper divisors (10123).

21850121 is an equidigital number, since it uses as much as digits as its factorization.

21850121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10122.

The product of its (nonzero) digits is 160, while the sum is 20.

The square root of 21850121 is about 4674.4112998323. The cubic root of 21850121 is about 279.5661691578.

Adding to 21850121 its reverse (12105812), we get a palindrome (33955933).

It can be divided in two parts, 21850 and 121, that multiplied together give a triangular number (2643850 = T₂₂₉₉).

The spelling of 21850121 in words is "twenty-one million, eight hundred fifty thousand, one hundred twenty-one".