21366789 has 4 divisors (see below), whose sum is σ = 28489056. Its totient is φ = 14244524.

The previous prime is 21366767. The next prime is 21366803. The reversal of 21366789 is 98766312.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21366789 - 2⁷ = 21366661 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21366789.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21366689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3561129 + ... + 3561134.

It is an arithmetic number, because the mean of its divisors is an integer number (7122264).

Almost surely, 2^21366789 is an apocalyptic number.

It is an amenable number.

21366789 is a deficient number, since it is larger than the sum of its proper divisors (7122267).

21366789 is an equidigital number, since it uses as much as digits as its factorization.

21366789 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7122266.

The product of its digits is 108864, while the sum is 42.

The square root of 21366789 is about 4622.4224168719. The cubic root of 21366789 is about 277.4894144164.

It can be divided in two parts, 21366 and 789, that added together give a triangular number (22155 = T₂₁₀).

The spelling of 21366789 in words is "twenty-one million, three hundred sixty-six thousand, seven hundred eighty-nine".