21124645 has 8 divisors (see below), whose sum is σ = 25417080. Its totient is φ = 16854720.

The previous prime is 21124643. The next prime is 21124657. The reversal of 21124645 is 54642112.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 349281 + 20775364 = 591^2 + 4558^2 .

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

It is not a de Polignac number, because 21124645 - 2¹ = 21124643 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21124643) 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, 3486 + ... + 7375.

It is an arithmetic number, because the mean of its divisors is an integer number (3177135).

Almost surely, 2^21124645 is an apocalyptic number.

It is an amenable number.

21124645 is a deficient number, since it is larger than the sum of its proper divisors (4292435).

21124645 is a wasteful number, since it uses less digits than its factorization.

21124645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11255.

The product of its digits is 1920, while the sum is 25.

The square root of 21124645 is about 4596.1554586415. The cubic root of 21124645 is about 276.4371921821.

Adding to 21124645 its reverse (54642112), we get a palindrome (75766757).

The spelling of 21124645 in words is "twenty-one million, one hundred twenty-four thousand, six hundred forty-five".