21623449 has 4 divisors (see below), whose sum is σ = 21641140. Its totient is φ = 21605760.

The previous prime is 21623423. The next prime is 21623471. The reversal of 21623449 is 94432612.

It is a happy number.

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 14197824 + 7425625 = 3768^2 + 2725^2 .

It is a cyclic number.

It is not a de Polignac number, because 21623449 - 2⁷ = 21623321 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21623449.

It is not an unprimeable number, because it can be changed into a prime (21623419) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 6864 + ... + 9505.

It is an arithmetic number, because the mean of its divisors is an integer number (5410285).

Almost surely, 2^21623449 is an apocalyptic number.

It is an amenable number.

21623449 is a deficient number, since it is larger than the sum of its proper divisors (17691).

21623449 is a wasteful number, since it uses less digits than its factorization.

21623449 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17690.

The product of its digits is 10368, while the sum is 31.

The square root of 21623449 is about 4650.1020418911. The cubic root of 21623449 is about 278.5960719190.

The spelling of 21623449 in words is "twenty-one million, six hundred twenty-three thousand, four hundred forty-nine".