21423505 has 8 divisors (see below), whose sum is σ = 26130024. Its totient is φ = 16857600.

The previous prime is 21423497. The next prime is 21423509. The reversal of 21423505 is 50532412.

It can be written as a sum of positive squares in 4 ways, for example, as 3207681 + 18215824 = 1791^2 + 4268^2 .

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

It is not a de Polignac number, because 21423505 - 2³ = 21423497 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21423509) 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, 34816 + ... + 35425.

It is an arithmetic number, because the mean of its divisors is an integer number (3266253).

Almost surely, 2^21423505 is an apocalyptic number.

It is an amenable number.

21423505 is a deficient number, since it is larger than the sum of its proper divisors (4706519).

21423505 is an equidigital number, since it uses as much as digits as its factorization.

21423505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 70307.

The product of its (nonzero) digits is 1200, while the sum is 22.

The square root of 21423505 is about 4628.5532296820. The cubic root of 21423505 is about 277.7347201113.

Adding to 21423505 its reverse (50532412), we get a palindrome (71955917).

The spelling of 21423505 in words is "twenty-one million, four hundred twenty-three thousand, five hundred five".