21513245 has 16 divisors (see below), whose sum is σ = 29438640. Its totient is φ = 14951424.

The previous prime is 21513241. The next prime is 21513251. The reversal of 21513245 is 54231512.

It can be written as a sum of positive squares in 8 ways, for example, as 737881 + 20775364 = 859^2 + 4558^2 .

It is a cyclic number.

It is not a de Polignac number, because 21513245 - 2² = 21513241 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21513245.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21513241) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8630 + ... + 10839.

It is an arithmetic number, because the mean of its divisors is an integer number (1839915).

Almost surely, 2^21513245 is an apocalyptic number.

It is an amenable number.

21513245 is a deficient number, since it is larger than the sum of its proper divisors (7925395).

21513245 is a wasteful number, since it uses less digits than its factorization.

21513245 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19504.

The product of its digits is 1200, while the sum is 23.

The square root of 21513245 is about 4638.2372729303. The cubic root of 21513245 is about 278.1219769061.

Adding to 21513245 its reverse (54231512), we get a palindrome (75744757).

The spelling of 21513245 in words is "twenty-one million, five hundred thirteen thousand, two hundred forty-five".