21109799 has 2 divisors, whose sum is σ = 21109800. Its totient is φ = 21109798.

The previous prime is 21109789. The next prime is 21109841. The reversal of 21109799 is 99790112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21109799 - 2¹² = 21105703 is a prime.

It is a super-2 number, since 2×21109799² = 891247227640802, which contains 22 as substring.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21109769) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10554899 + 10554900.

It is an arithmetic number, because the mean of its divisors is an integer number (10554900).

Almost surely, 2^21109799 is an apocalyptic number.

21109799 is a deficient number, since it is larger than the sum of its proper divisors (1).

21109799 is an equidigital number, since it uses as much as digits as its factorization.

21109799 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10206, while the sum is 38.

The square root of 21109799 is about 4594.5401293274. The cubic root of 21109799 is about 276.3724187334.

The spelling of 21109799 in words is "twenty-one million, one hundred nine thousand, seven hundred ninety-nine".