21811641 has 4 divisors (see below), whose sum is σ = 29082192. Its totient is φ = 14541092.

The previous prime is 21811637. The next prime is 21811661. The reversal of 21811641 is 14611812.

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 21811641 - 2² = 21811637 is a prime.

It is a super-2 number, since 2×21811641² = 951495366225762, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21811661) 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, 3635271 + ... + 3635276.

It is an arithmetic number, because the mean of its divisors is an integer number (7270548).

Almost surely, 2^21811641 is an apocalyptic number.

It is an amenable number.

21811641 is a deficient number, since it is larger than the sum of its proper divisors (7270551).

21811641 is an equidigital number, since it uses as much as digits as its factorization.

21811641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7270550.

The product of its digits is 384, while the sum is 24.

The square root of 21811641 is about 4670.2934597303. The cubic root of 21811641 is about 279.4019591219.

The spelling of 21811641 in words is "twenty-one million, eight hundred eleven thousand, six hundred forty-one".