21999959 has 4 divisors (see below), whose sum is σ = 22009416. Its totient is φ = 21990504.

The previous prime is 21999917. The next prime is 21999973. The reversal of 21999959 is 95999912.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21999959 - 2²⁰ = 20951383 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21999959.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21999059) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1472 + ... + 6794.

It is an arithmetic number, because the mean of its divisors is an integer number (5502354).

Almost surely, 2^21999959 is an apocalyptic number.

21999959 is a deficient number, since it is larger than the sum of its proper divisors (9457).

21999959 is an equidigital number, since it uses as much as digits as its factorization.

21999959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9456.

The product of its digits is 590490, while the sum is 53.

The square root of 21999959 is about 4690.4113892067. The cubic root of 21999959 is about 280.2037589994.

The spelling of 21999959 in words is "twenty-one million, nine hundred ninety-nine thousand, nine hundred fifty-nine".