21388899 has 16 divisors (see below), whose sum is σ = 32657408. Its totient is φ = 12197952.

The previous prime is 21388897. The next prime is 21388943. The reversal of 21388899 is 99888312.

It is a happy number.

It is not a de Polignac number, because 21388899 - 2¹ = 21388897 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21388891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19134 + ... + 20220.

It is an arithmetic number, because the mean of its divisors is an integer number (2041088).

Almost surely, 2^21388899 is an apocalyptic number.

21388899 is a deficient number, since it is larger than the sum of its proper divisors (11268509).

21388899 is a wasteful number, since it uses less digits than its factorization.

21388899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2034.

The product of its digits is 248832, while the sum is 48.

The square root of 21388899 is about 4624.8134016412. The cubic root of 21388899 is about 277.5850952405.

The spelling of 21388899 in words is "twenty-one million, three hundred eighty-eight thousand, eight hundred ninety-nine".