21809799 has 12 divisors (see below), whose sum is σ = 34367112. Its totient is φ = 13218000.

The previous prime is 21809789. The next prime is 21809863. The reversal of 21809799 is 99790812.

It is not a de Polignac number, because 21809799 - 2⁹ = 21809287 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21809719) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 110052 + ... + 110249.

It is an arithmetic number, because the mean of its divisors is an integer number (2863926).

Almost surely, 2^21809799 is an apocalyptic number.

21809799 is a deficient number, since it is larger than the sum of its proper divisors (12557313).

21809799 is a wasteful number, since it uses less digits than its factorization.

21809799 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 220318 (or 220315 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 45.

The square root of 21809799 is about 4670.0962516848. The cubic root of 21809799 is about 279.3940937058.

The spelling of 21809799 in words is "twenty-one million, eight hundred nine thousand, seven hundred ninety-nine".