21623345 has 4 divisors (see below), whose sum is σ = 25948020. Its totient is φ = 17298672.

The previous prime is 21623321. The next prime is 21623347. The reversal of 21623345 is 54332612.

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

It can be written as a sum of positive squares in 2 ways, for example, as 16096144 + 5527201 = 4012^2 + 2351^2 .

It is a cyclic number.

It is not a de Polignac number, because 21623345 - 2²⁴ = 4846129 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21623347) 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, 2162330 + ... + 2162339.

It is an arithmetic number, because the mean of its divisors is an integer number (6487005).

Almost surely, 2^21623345 is an apocalyptic number.

It is an amenable number.

21623345 is a deficient number, since it is larger than the sum of its proper divisors (4324675).

21623345 is an equidigital number, since it uses as much as digits as its factorization.

21623345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4324674.

The product of its digits is 4320, while the sum is 26.

The square root of 21623345 is about 4650.0908593274. The cubic root of 21623345 is about 278.5956252737.

Adding to 21623345 its reverse (54332612), we get a palindrome (75955957).

The spelling of 21623345 in words is "twenty-one million, six hundred twenty-three thousand, three hundred forty-five".