21667841 has 4 divisors (see below), whose sum is σ = 23334612. Its totient is φ = 20001072.

The previous prime is 21667837. The next prime is 21667859. The reversal of 21667841 is 14876612.

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 11587216 + 10080625 = 3404^2 + 3175^2 .

It is not a de Polignac number, because 21667841 - 2² = 21667837 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21667861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 833366 + ... + 833391.

It is an arithmetic number, because the mean of its divisors is an integer number (5833653).

It is a Proth number, since it is equal to 2645 ⋅ 2¹³ + 1 and 2645 < 2¹³.

Almost surely, 2^21667841 is an apocalyptic number.

It is an amenable number.

21667841 is a deficient number, since it is larger than the sum of its proper divisors (1666771).

21667841 is a wasteful number, since it uses less digits than its factorization.

21667841 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1666770.

The product of its digits is 16128, while the sum is 35.

The square root of 21667841 is about 4654.8728231822. The cubic root of 21667841 is about 278.7865901414.

The spelling of 21667841 in words is "twenty-one million, six hundred sixty-seven thousand, eight hundred forty-one".