21388099 has 2 divisors, whose sum is σ = 21388100. Its totient is φ = 21388098.

The previous prime is 21388049. The next prime is 21388117. The reversal of 21388099 is 99088312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21388099 - 2¹³ = 21379907 is a prime.

It is not a weakly prime, because it can be changed into another prime (21388009) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10694049 + 10694050.

It is an arithmetic number, because the mean of its divisors is an integer number (10694050).

Almost surely, 2^21388099 is an apocalyptic number.

21388099 is a deficient number, since it is larger than the sum of its proper divisors (1).

21388099 is an equidigital number, since it uses as much as digits as its factorization.

21388099 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 40.

The square root of 21388099 is about 4624.7269108565. The cubic root of 21388099 is about 277.5816343978.

The spelling of 21388099 in words is "twenty-one million, three hundred eighty-eight thousand, ninety-nine".