21085199 has 4 divisors (see below), whose sum is σ = 21430920. Its totient is φ = 20739480.

The previous prime is 21085171. The next prime is 21085201. The reversal of 21085199 is 99158012.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21085199 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21085109) 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, 172769 + ... + 172890.

It is an arithmetic number, because the mean of its divisors is an integer number (5357730).

Almost surely, 2^21085199 is an apocalyptic number.

21085199 is a deficient number, since it is larger than the sum of its proper divisors (345721).

21085199 is an equidigital number, since it uses as much as digits as its factorization.

21085199 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 345720.

The product of its (nonzero) digits is 6480, while the sum is 35.

The square root of 21085199 is about 4591.8622583871. The cubic root of 21085199 is about 276.2650214664.

The spelling of 21085199 in words is "twenty-one million, eighty-five thousand, one hundred ninety-nine".