21421811 has 4 divisors (see below), whose sum is σ = 21445800. Its totient is φ = 21397824.

The previous prime is 21421793. The next prime is 21421817. The reversal of 21421811 is 11812412.

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

It is a cyclic number.

It is not a de Polignac number, because 21421811 - 2⁶ = 21421747 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21421817) 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, 10601 + ... + 12458.

It is an arithmetic number, because the mean of its divisors is an integer number (5361450).

Almost surely, 2^21421811 is an apocalyptic number.

21421811 is a deficient number, since it is larger than the sum of its proper divisors (23989).

21421811 is an equidigital number, since it uses as much as digits as its factorization.

21421811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23988.

The product of its digits is 128, while the sum is 20.

The square root of 21421811 is about 4628.3702315178. The cubic root of 21421811 is about 277.7273995691.

The spelling of 21421811 in words is "twenty-one million, four hundred twenty-one thousand, eight hundred eleven".