21013999 has 4 divisors (see below), whose sum is σ = 21301936. Its totient is φ = 20726064.

The previous prime is 21013997. The next prime is 21014041. The reversal of 21013999 is 99931012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21013999 - 2¹ = 21013997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013991) 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 3 ways as a sum of consecutive naturals, for example, 143859 + ... + 144004.

It is an arithmetic number, because the mean of its divisors is an integer number (5325484).

Almost surely, 2^21013999 is an apocalyptic number.

21013999 is a deficient number, since it is larger than the sum of its proper divisors (287937).

21013999 is an equidigital number, since it uses as much as digits as its factorization.

21013999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 287936.

The product of its (nonzero) digits is 4374, while the sum is 34.

The square root of 21013999 is about 4584.1028566122. The cubic root of 21013999 is about 275.9537090677.

The spelling of 21013999 in words is "twenty-one million, thirteen thousand, nine hundred ninety-nine".