21785423 has 8 divisors (see below), whose sum is σ = 23832576. Its totient is φ = 19749400.

The previous prime is 21785377. The next prime is 21785437. The reversal of 21785423 is 32458712.

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

It is not a de Polignac number, because 21785423 - 2¹⁴ = 21769039 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21785423.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21785123) 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, 1628 + ... + 6798.

It is an arithmetic number, because the mean of its divisors is an integer number (2979072).

Almost surely, 2^21785423 is an apocalyptic number.

21785423 is a deficient number, since it is larger than the sum of its proper divisors (2047153).

21785423 is a wasteful number, since it uses less digits than its factorization.

21785423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5565.

The product of its digits is 13440, while the sum is 32.

The square root of 21785423 is about 4667.4857257414. The cubic root of 21785423 is about 279.2899654453.

Subtracting 21785423 from its reverse (32458712), we obtain a square (10673289 = 3267²).

The spelling of 21785423 in words is "twenty-one million, seven hundred eighty-five thousand, four hundred twenty-three".