21307899 has 4 divisors (see below), whose sum is σ = 28410536. Its totient is φ = 14205264.

The previous prime is 21307889. The next prime is 21307901. The reversal of 21307899 is 99870312.

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

It is not a de Polignac number, because 21307899 - 2⁷ = 21307771 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21307829) 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, 3551314 + ... + 3551319.

It is an arithmetic number, because the mean of its divisors is an integer number (7102634).

Almost surely, 2^21307899 is an apocalyptic number.

21307899 is a deficient number, since it is larger than the sum of its proper divisors (7102637).

21307899 is an equidigital number, since it uses as much as digits as its factorization.

21307899 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7102636.

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 21307899 is about 4616.0479850192. The cubic root of 21307899 is about 277.2342460225.

The spelling of 21307899 in words is "twenty-one million, three hundred seven thousand, eight hundred ninety-nine".