21100399 has 2 divisors, whose sum is σ = 21100400. Its totient is φ = 21100398.

The previous prime is 21100381. The next prime is 21100403. The reversal of 21100399 is 99300112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21100399 - 2⁹ = 21099887 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21100319) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550199 + 10550200.

It is an arithmetic number, because the mean of its divisors is an integer number (10550200).

Almost surely, 2^21100399 is an apocalyptic number.

21100399 is a deficient number, since it is larger than the sum of its proper divisors (1).

21100399 is an equidigital number, since it uses as much as digits as its factorization.

21100399 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 486, while the sum is 25.

The square root of 21100399 is about 4593.5170621214. The cubic root of 21100399 is about 276.3313906080.

It can be divided in two parts, 2 and 1100399, that added together give a square (1100401 = 1049²).

The spelling of 21100399 in words is "twenty-one million, one hundred thousand, three hundred ninety-nine".