21251513 has 8 divisors (see below), whose sum is σ = 22604832. Its totient is φ = 19909696.

The previous prime is 21251491. The next prime is 21251533. The reversal of 21251513 is 31515212.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21251513 - 2⁸ = 21251257 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21251533) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1106 + ... + 6612.

It is an arithmetic number, because the mean of its divisors is an integer number (2825604).

Almost surely, 2^21251513 is an apocalyptic number.

It is an amenable number.

21251513 is a deficient number, since it is larger than the sum of its proper divisors (1353319).

21251513 is a wasteful number, since it uses less digits than its factorization.

21251513 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5751.

The product of its digits is 300, while the sum is 20.

The square root of 21251513 is about 4609.9363336168. The cubic root of 21251513 is about 276.9894864095.

Adding to 21251513 its reverse (31515212), we get a palindrome (52766725).

The spelling of 21251513 in words is "twenty-one million, two hundred fifty-one thousand, five hundred thirteen".