21423506 has 8 divisors (see below), whose sum is σ = 34607244. Its totient is φ = 9887760.

The previous prime is 21423497. The next prime is 21423509. The reversal of 21423506 is 60532412.

It can be written as a sum of positive squares in 2 ways, for example, as 21242881 + 180625 = 4609^2 + 425^2 .

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

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 3 ways as a sum of consecutive naturals, for example, 411965 + ... + 412016.

Almost surely, 2^21423506 is an apocalyptic number.

21423506 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21423506 is a deficient number, since it is larger than the sum of its proper divisors (13183738).

21423506 is a wasteful number, since it uses less digits than its factorization.

21423506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 823996.

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 21423506 is about 4628.5533377072. The cubic root of 21423506 is about 277.7347244326.

Adding to 21423506 its reverse (60532412), we get a palindrome (81955918).

The spelling of 21423506 in words is "twenty-one million, four hundred twenty-three thousand, five hundred six".