21800091 has 4 divisors (see below), whose sum is σ = 29066792. Its totient is φ = 14533392.

The previous prime is 21800089. The next prime is 21800101. The reversal of 21800091 is 19000812.

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

It is not a de Polignac number, because 21800091 - 2¹ = 21800089 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21800081) 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, 3633346 + ... + 3633351.

It is an arithmetic number, because the mean of its divisors is an integer number (7266698).

Almost surely, 2^21800091 is an apocalyptic number.

21800091 is a deficient number, since it is larger than the sum of its proper divisors (7266701).

21800091 is an equidigital number, since it uses as much as digits as its factorization.

21800091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7266700.

The product of its (nonzero) digits is 144, while the sum is 21.

The square root of 21800091 is about 4669.0567569906. The cubic root of 21800091 is about 279.3526328254.

The spelling of 21800091 in words is "twenty-one million, eight hundred thousand, ninety-one".