21315445 has 8 divisors (see below), whose sum is σ = 26403840. Its totient is φ = 16502160.

The previous prime is 21315443. The next prime is 21315451. The reversal of 21315445 is 54451312.

It is a happy number.

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

It is not a de Polignac number, because 21315445 - 2¹ = 21315443 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21315443) 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, 68605 + ... + 68914.

It is an arithmetic number, because the mean of its divisors is an integer number (3300480).

Almost surely, 2^21315445 is an apocalyptic number.

It is an amenable number.

21315445 is a deficient number, since it is larger than the sum of its proper divisors (5088395).

21315445 is a wasteful number, since it uses less digits than its factorization.

21315445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 137555.

The product of its digits is 2400, while the sum is 25.

The square root of 21315445 is about 4616.8652785196. The cubic root of 21315445 is about 277.2669688281.

Adding to 21315445 its reverse (54451312), we get a palindrome (75766757).

The spelling of 21315445 in words is "twenty-one million, three hundred fifteen thousand, four hundred forty-five".