21989559 has 4 divisors (see below), whose sum is σ = 29319416. Its totient is φ = 14659704.

The previous prime is 21989557. The next prime is 21989579. The reversal of 21989559 is 95598912.

It is a happy number.

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

It is not a de Polignac number, because 21989559 - 2¹ = 21989557 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 (21989557) 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, 3664924 + ... + 3664929.

It is an arithmetic number, because the mean of its divisors is an integer number (7329854).

Almost surely, 2^21989559 is an apocalyptic number.

21989559 is a deficient number, since it is larger than the sum of its proper divisors (7329857).

21989559 is an equidigital number, since it uses as much as digits as its factorization.

21989559 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7329856.

The product of its digits is 291600, while the sum is 48.

The square root of 21989559 is about 4689.3026133957. The cubic root of 21989559 is about 280.1595986381.

The spelling of 21989559 in words is "twenty-one million, nine hundred eighty-nine thousand, five hundred fifty-nine".