21398899 has 2 divisors, whose sum is σ = 21398900. Its totient is φ = 21398898.

The previous prime is 21398873. The next prime is 21398917. The reversal of 21398899 is 99889312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21398899 - 2¹⁹ = 20874611 is a prime.

It is not a weakly prime, because it can be changed into another prime (21398849) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10699449 + 10699450.

It is an arithmetic number, because the mean of its divisors is an integer number (10699450).

Almost surely, 2^21398899 is an apocalyptic number.

21398899 is a deficient number, since it is larger than the sum of its proper divisors (1).

21398899 is an equidigital number, since it uses as much as digits as its factorization.

21398899 is an evil number, because the sum of its binary digits is even.

The product of its digits is 279936, while the sum is 49.

The square root of 21398899 is about 4625.8944000053. The cubic root of 21398899 is about 277.6283484948.

The spelling of 21398899 in words is "twenty-one million, three hundred ninety-eight thousand, eight hundred ninety-nine".