21312089 has 4 divisors (see below), whose sum is σ = 21330660. Its totient is φ = 21293520.

The previous prime is 21312079. The next prime is 21312107. The reversal of 21312089 is 98021312.

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

It can be written as a sum of positive squares in 2 ways, for example, as 20322064 + 990025 = 4508^2 + 995^2 .

It is a cyclic number.

It is not a de Polignac number, because 21312089 - 2¹⁶ = 21246553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21312019) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7442 + ... + 9899.

It is an arithmetic number, because the mean of its divisors is an integer number (5332665).

Almost surely, 2^21312089 is an apocalyptic number.

It is an amenable number.

21312089 is a deficient number, since it is larger than the sum of its proper divisors (18571).

21312089 is a wasteful number, since it uses less digits than its factorization.

21312089 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18570.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 21312089 is about 4616.5018141446. The cubic root of 21312089 is about 277.2524166762.

The spelling of 21312089 in words is "twenty-one million, three hundred twelve thousand, eighty-nine".