21861841 has 4 divisors (see below), whose sum is σ = 21942784. Its totient is φ = 21780900.

The previous prime is 21861839. The next prime is 21861859. The reversal of 21861841 is 14816812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21861841 - 2¹ = 21861839 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21861341) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 40065 + ... + 40606.

It is an arithmetic number, because the mean of its divisors is an integer number (5485696).

Almost surely, 2^21861841 is an apocalyptic number.

It is an amenable number.

21861841 is a deficient number, since it is larger than the sum of its proper divisors (80943).

21861841 is an equidigital number, since it uses as much as digits as its factorization.

21861841 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80942.

The product of its digits is 3072, while the sum is 31.

The square root of 21861841 is about 4675.6647655708. The cubic root of 21861841 is about 279.6161449277.

The spelling of 21861841 in words is "twenty-one million, eight hundred sixty-one thousand, eight hundred forty-one".