21042389 has 8 divisors (see below), whose sum is σ = 21650328. Its totient is φ = 20439040.

The previous prime is 21042383. The next prime is 21042407. The reversal of 21042389 is 98324012.

It can be written as a sum of positive squares in 4 ways, for example, as 339889 + 20702500 = 583^2 + 4550^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21042389 - 2¹² = 21038293 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 (21042383) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9539 + ... + 11535.

It is an arithmetic number, because the mean of its divisors is an integer number (2706291).

Almost surely, 2^21042389 is an apocalyptic number.

It is an amenable number.

21042389 is a deficient number, since it is larger than the sum of its proper divisors (607939).

21042389 is a wasteful number, since it uses less digits than its factorization.

21042389 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2295.

The product of its (nonzero) digits is 3456, while the sum is 29.

The square root of 21042389 is about 4587.1983824552. The cubic root of 21042389 is about 276.0779246819.

The spelling of 21042389 in words is "twenty-one million, forty-two thousand, three hundred eighty-nine".