21775423 has 4 divisors (see below), whose sum is σ = 22477888. Its totient is φ = 21072960.

The previous prime is 21775417. The next prime is 21775427. The reversal of 21775423 is 32457712.

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

It is a cyclic number.

It is not a de Polignac number, because 21775423 - 2¹³ = 21767231 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31), and also a Moran number because the ratio is a prime number: 702433 = 21775423 / (2 + 1 + 7 + 7 + 5 + 4 + 2 + 3).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21775427) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 351186 + ... + 351247.

It is an arithmetic number, because the mean of its divisors is an integer number (5619472).

Almost surely, 2^21775423 is an apocalyptic number.

21775423 is a deficient number, since it is larger than the sum of its proper divisors (702465).

21775423 is an equidigital number, since it uses as much as digits as its factorization.

21775423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 702464.

The product of its digits is 11760, while the sum is 31.

The square root of 21775423 is about 4666.4143622272. The cubic root of 21775423 is about 279.2472254429.

The spelling of 21775423 in words is "twenty-one million, seven hundred seventy-five thousand, four hundred twenty-three".