21390789 has 16 divisors (see below), whose sum is σ = 34311680. Its totient is φ = 11579760.

The previous prime is 21390767. The next prime is 21390791. The reversal of 21390789 is 98709312.

It is not a de Polignac number, because 21390789 - 2¹³ = 21382597 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390289) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26407 + ... + 27204.

It is an arithmetic number, because the mean of its divisors is an integer number (2144480).

Almost surely, 2^21390789 is an apocalyptic number.

It is an amenable number.

21390789 is a deficient number, since it is larger than the sum of its proper divisors (12920891).

21390789 is a wasteful number, since it uses less digits than its factorization.

21390789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53640.

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

The square root of 21390789 is about 4625.0177296957. The cubic root of 21390789 is about 277.5932711386.

The spelling of 21390789 in words is "twenty-one million, three hundred ninety thousand, seven hundred eighty-nine".