21404523 has 24 divisors (see below), whose sum is σ = 34350480. Its totient is φ = 11807040.

The previous prime is 21404503. The next prime is 21404531. The reversal of 21404523 is 32540412.

It is not a de Polignac number, because 21404523 - 2⁵ = 21404491 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a self number, because there is not a number n which added to its sum of digits gives 21404523.

It is not an unprimeable number, because it can be changed into a prime (21404503) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1753 + ... + 6773.

It is an arithmetic number, because the mean of its divisors is an integer number (1431270).

Almost surely, 2^21404523 is an apocalyptic number.

21404523 is a deficient number, since it is larger than the sum of its proper divisors (12945957).

21404523 is a wasteful number, since it uses less digits than its factorization.

21404523 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5067 (or 5060 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 21.

The square root of 21404523 is about 4626.5022425154. The cubic root of 21404523 is about 277.6526682050.

Adding to 21404523 its reverse (32540412), we get a palindrome (53944935).

The spelling of 21404523 in words is "twenty-one million, four hundred four thousand, five hundred twenty-three".